Help! 1966 GT Fastback validation. Just Bought

I thought you would be able to get the info from the VIN, but in looking at the Mustang Recognition Guide, no such luck. It does say the grill is blacked out (not chrome) and the running horse has extensions with dual fog lamps. Other changes on the GT include no rocker panel moldings--replaced with a GT stripe, no simulated air scoops, running horse emblem behind the front wheel well replaced with a GT emblem, dual exhaust, front discs, and a GT gas cap.

Okay, here;s my 2 cts. It looks like a unmolested 66 gt, so you need to decide whether to keep it original where it has the most value, or to make changes and/or mods, if you do, then I would save every part you take off, so if you do decide to sell it later the new owner might want to make it original again. Just looking at the pics, your GT emblem on the back is your gas cap and I don't see the filler neck for the tank, some when working on the car, turn the filler neck inside the tank and put the gas cap back on, until they are done with whatever repairs they are doing in the rear of the car. It also looks like you need to reupholster at least the front bucket seats. It has fog lights and a/c both good options, the a/c may only need the o-rings replaced and freoned up unless the front seal is bad in the compressor, those compressors are as rugged as they get. Is that just dirt on the paint or is it worn off, if it is just dirt, Then I would wash it and use a good paste wax. Any rust needs to be addressed, either removed and patched or at least sealed until a later date to fix it right. And you can pat yourself on the back, it looks great for a 49 year old car.
I decoded your door tag using my books and I come up with some discrepancies, you should compare the serial number stamped onto the fender apron by the shock tower on the drivers side to verify the door plate is the one for this vehicle, if it had been wrecked before on a drivers door they would just change the door and not transfer the plate, I will list the decode and note the ones I found:

Body- 63A- 2 door Fastback standard bucket seats
Color-R- Ivy green or Dark Green Metallic (my books differ)
Trim-26-Interior Black
Date- 03J- September 03 (1966)
DSO-65-Oklahoma City
Axle-A-3.00:1 axle Equa-Lock Differential (this is an option, I would look at the tag on the differential to hopefully verify it, the only other way, is to drive the car like on a wet surface, and spin the rear tires, the differential will lock up so both wheels are together, to unlock, back the car up several feet and the rear axle will unlock the tires, normally this axle acts just like a normal axle otherwise. These are great rear axles)
Trans-5- 4 speed manual (It looks like you have an automatic C4 which should be a code of 6)

Serial number
6- 1966
R-San Jose Assembly plant
09-Fastback
A-289 4v premium fuel
104583-serial number (mustangs, falcons, and fairlanes combined in this)

Good Luck. One real upgrade, I recommend is to change the brake master cylinder to a dual-chamber design like on the 1967 mustang, as with the single chamber like you have, is if you develop a brake leak, and loose the fluid (you won't know till it is gone) you will have no brakes, and will have to use the parking brake to stop the car, been there and done that many times, I have since upgraded my 65 to a 67 dual chamber. If you are going to keep the car original and have it judged in shows, then I would leave the MC alone.

Another good way to verify a factory GT car is to remove the back seat. There will additional reinforcement plates welded in. This was to support the dual exhaust. Most of the GT cars you see were dealer prepped cars. They put on the disc brakes and other easy items and sold them as GT Mustangs. The brake line will also have been moved to accommodate the dual exhaust. The automatic bugs me. I thought automatic GT Stangs didn't come out until 67. Feel free to correct me anyone

Hello Greg,

Welcome to AFM.

Is it a real GT? From pictures no one can tell you but as Rex indicated it seems to be 'original' enough that it could well be a factory GT. 20-30 years ago being a GT didn't make much of difference to anyone except that they had stripes.

There was no restriction on transmissions for a GT as there was for a K-code engined car. By '66 you could have any transmission with any engine; even a C4 automatic behind a HiPo. What's in the car may well be wrong but a GT could have had any transmission. Since its coded as a 4-speed, the car could well have had a T-10 when new like our San Jose GT. If so, the '66 T-10 had some 66-only, Ford-only differences that many owners and even mechanics didn't understand; then or now. They may have thought it easier to swap in a C4 then to fix the T-10 correctly? That is how we got our GT; the prior owner couldn't make the tranny work right so he sold the car.

An Equa-Loc rear end was the only 'limited slip' offering in 1966. It was simply a set of clutch discs inside that makes turning one wheel by itself difficult. It should always take 100 ft-lb of torque to turn one rear wheel by itself. There is no actual 'locking', the system simply added a friction clutch to the rear axle. Since it doesn't lock, there is also nothing to unlock. If it acts like a normal axle then the clutch discs are shot.

After all these years is unlikely those clutches are still working but wore out from normal use while Nixon was president. The one I bought in 1980 was so worn out that, except for the ID tag, there was no indication that it was an Equa-Loc. In those days Ford still sold the clutch discs ($22 for the set) which I replaced so that mine works as new. Those discs have been NLA for many years and if you are want to repair one of them today you will have to use some automatic transmission clutch discs of similar size.

There was nothing special about the carb on an A-code engine other than it was a 4-barrel Autolite so I don't understand why anyone went to the trouble of stealing it? If it had been a HiPo carb then those are quite rare and valuable today.

Unlike the early Thunderbirds in the 50s, the sequential number in your VIN was a count of Mustangs ONLY and each assembly plant had their own running total. Since each year the numbers started over again at 100,000 your number indicates that San Jose had only built 4,583 '66 Mustangs which agrees with the early MY66 production date of Sept 1965.

Thanks guys! Good information. I'll try to crawl under tonight and look for signs of an originally equipped 4 speed in addition to removing the back seat to look for the bracing. Life has been so crazy the last couple days that I haven't had time to even wash it off.

I very much appreciate originality and plan to keep this all together as it sits assuming the engine runs. If the engine needs rebuilt then I will have a hard time not dropping in a 5.0/6 speed. But it's just so clean and really should be kept original. Regardless I do not plan to paint the car at this time anytime soon. I love cars I can drive/enjoy for what they are.

From what I can see even the glove box door looks like a GT door. If they would have changed it over at the dealership more than likely they wouldn't have taken the time to change out a perfectly good glove box door?

Not all GT glove box doors were different. Yours looks like its the 'GT' one but ours is a normal glove box door. If not all, then I would say that most GTs were built at the factory since swapping disc brakes, front roll bar and a steering gear box is NOT an easy job to do for a car that wasn't all that much more valuable than a normal Mustang. They could always order another one if they needed a GT; delivery time was about a month in 1966.

The under-seat reinforcements were on any dual-exhast car so are not specific to a GT. A GT is a collection of things that you have to consider.

http://www.mustangdreams.com/Verify-1965-1966-Mustang-GT.htm

Looks like a great catch and a great early Mustang to start with! Lucky you!
As for GT id's I believe there is also reinforcments in the rear frame rails for use with the dual exhaust hardware, right near the tialpipes.. There are many articles out there for other specific facts on GT's. Looks like the car has been repainted or maybe just the drivers door as there appears to be overspray on the door latch and edge of the door tag?

Either way a nice find and awesome car even if it turns out not to be a GT. Let's hope it is! Welcome!

Congrats on the find, you are indeed a...

Ivy66GT and everyone else... thanks for the info!


Car was purchased in 1984 and the son drove it until 1988 when they did a mini restoration with a repainted/new interior/motor rebuild. Tom said there was never an accident or any damage, the paint was just tired.

Is the car being a GT really that big of a deal compared to a regular fast back A code?


Does anyone have a 4-barrel Autolite laying around they would want to sell? Prefer date coded correct but will take any to get it running.

10+ years ago I found this Mustang and a '63 fuel injected Corvette convertible two miles away from this car. The vette is still setting outside. Rotting. The fiberglass is now in pretty sad shape and the house is falling down around it. So sad. I even offered to put a new roof on the house and pay $ on top to purchase the vette. Guess some people just want water in the house vs getting rid of a car that hasn't ran in decades. Fortunately this one won't end up w/ the same fate.

t_towner said:

Is the car being a GT really that big of a deal compared to a regular fast back A code?

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IMHO, not really. Disc brakes is the biggest plus and the quicker steering doesn't hurt. But you are never going to confuse its handling for a '66 Porsche.

When new, the 4V engine was a $52 option over the 2V. The GT option was an extra $100 over simply having a 4V engine. Your A/C system at $310 cost THREE times the GT package. Considering your car was pushing $3500 an extra $100 was almost in the noise. Today the market values the GT package as worth around 10% more. The relative value of the A/C and GT package has been reversed in today's market. It makes those shiny exhaust trumpets pretty valuable today.

Here's the Decode in accordance to the Dataplate information.
Unfortunately, there has never been a way of defining whether a car is a genuine GT or not. This one has everything visually from the outside, that a GT should have.

Great find.

1966 Mustang VIN/Dataplate Info
Dataplate Breakdown:
Body: Fastback, Standard Interior, Bucket Seats
Color: Dark Metallic Green
[Interior] Trim: Black
Date: 03 of September (1st year)
DSO: Oklahoma City
Axle: 3.00:1 Limited-Slip
Trans: 4-Speed Manual

VIN (Warrenty Number) Breakdown:
6 = 1966
R = San Jose, CA
09 = Fastback
A = 289-4v
104583 = Consecutive unit number #104583

66 Fastback Work

Hi Wayne...I just ran across your thread about the 66. It could be identical to the one I just finished up, with a few notable exceptions.

The paint on mine (same dark ivy green) was, as you aptly describe, "tired out". I like the description! Ford had a problem with that color; the paint seemed to sort of blow off in the wind, at least in the sunny south.

Your carb question--did you get it resolved? My resto resulted in a spare Autolite carb which was working when the car expired 20 or so years ago. I also have various motor parts and other odds and ends which are likely serviceable and original but show some wear and tear. Let me know what you may need...can't ever tell whether my junk could be your salvation!

Charlie Jones
Hendersonville, TN

My 66 Mustang Paint Color

tlm69 said:

Nice car Charlie. I am planning a future respray of my 68 coupe which was originally highland green. Looking for a similar but updated color. Can you tell me what paint is on this car?

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Hey Tim, thanks for the car kudos! The color is compliments of a 94 Corvette, website Web Hosting - This site is temporarily unavailable Polo Green Metallic OEM Code 45, GM code 9539, Ditzler/PPG 4301, DuPont B9012.

Here's a 'Vette with the color, which appears to be true color, at least on my monitor... http://images.gtcarlot.com/pictures/22997162.jpg.

It's a little hard to shoot, according to my paint guy, due to the heavy metallic, had to work all the way across a body panel continuously--not hard to do except for the roof--otherwise there was an exposed trail of metal flake at the interface. But he did well.

Good luck.