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Discussion Starter #1
Ok I know that this topic has been covered more than probably anything else haha but I can not find this specific answer so I figured I would just ask.
I found a 89 foxbody roller with an 8.8" rear end 5 lug everything. Will that fit the 66 to convert to? its in decent shape and he wants 400 for the car with it and thats cheaper than I can find any of the rear ends alone.

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Hello CBowman;

I got carried away answering your question, sorry, lol.

WIDTH - Your housing is 57.25” wide from outside of axles. The 86 – 93 fox body is 59.25”. This means that if you want to have the same tire width/track, you need to install rims that have 1” more backspace/offset than the factory ones. Consider this especially when installing wide rims like 7 or 8’s.

8.8 SPRING MOUNTS/HOUSING PREP – Die grind off the 8.8 spring mounts and brackets. Leave the brake line mounting brackets?

DETERMINE WHAT SPRING MOUNTS ARE NEEDED - Measure the od of the axle tube where the spring mounts are on on your 66 then measure the 8.8. if the 8.8 is the same od then buy new 64 - 66 mounts. if the 8.8 is larger than buy 68 mounts and lower shock/spring mounting plates.

Ok, here’s the fun part, good luck. If anyone sees something I missed please post corrections.

WARNING - If you are not an experienced welder please have someone that is weld the brackets on.


DETERMINE PINION ANGLE - Unless someone here knows the pinion angle, you need to put the put your current housing on some jack stands so the perches are facing upward.

Turn the yoke until it is vertical

Place a floor jack under the yoke and make it approximately horizontal.

Take a 12” – 14” long level and make the housing level.

Place the level on clean perches and make them level by moving the jack up or down…duhh, lol.

Measure the distance from the center of the yoke to the ground.

Measure the distance from the outside of the mount to the mount to the outside of the flange on the housing.

Write those measurements down.


Set up the 8.8 on the jacks exactly the same way with the pinion at the same angle.

Take your mount measurement and put it on the 8.8

Hold your mount in with the place with the level on it and have a friend hold a 10” – 12” square on the outside of the mount.

Level the mount front to rear and square it and tack weld it.

Ok now, place the level on the mount horizontal to the axle and make sure it is level in that direction.

Recheck front to rear level then tack weld kitty corner to your first weld.

Check the mount again, if ok put around a tack weld 1/4" - 1/2" away from the two existing welds.

Check it again and if it’s ok put a 1/2" long weld on each corner starting on the corners opposite the existing tacks.

Do the same on the corners with the tack welds.

do the other mount the same way now.

Go back and finish welding first mount, then finish the other mount.

ANGLE FINDER/INCLINOMETER - If you want, you can buy an angle finder/inclinometer at the hardware store and use it for finding the angle of the pinion. If the distance from the center of the axle to the center of the u joint is different between the two diffs then your spring perch angle will be off a hair if you use the tape measure however this amount is so small that it is insignificant.

DRIVE SHAFT MOUNT - There are adapters to mount your driveshaft to the 8.8 flange plate or yokes that will fit if you remove the flange. You need to change the flange to a yoke style simply because I do not like the look of the flange.


The left tag is 1963 thru 1983 and the right tag is 1984 thru 2001.


Ford Rear Axle Assembly Identification - Page 13 -



137 Posts
^^^^Lots of good stuff there but the main thing is the 8.8 is not a bolt in. Foxbody cars use coil springs, the 66 coupe uses leafs. It has been swapped into a first gen body before but it's not for an amateur. (no offense don't know your background) If you're swapping from 4 lug to 5 lug you have a 6 cylinder car. There's more to it than just swapping rear ends and front brakes. You need the v8 mustang spindles, brakes, inner/outer tie rods, center link, and idler arm. The front springs are also 6 cylinder specific. I'm not sure what your exact plans are but if you're swapping to a v8 you definitely are going to want some heavier springs over the stock 6 cylinder ones.
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