Tom Sheahan emailed me and I decided to post his question so some opionions will come from this Frank.GT50

I am looking to autocross the car, and maybe (after I figure how to put a cage in it) do some wheel to wheel.
I am not looking to go pro with the thing, I just want a budget oriented V8 with good car balance and brakes. The stock brakes left something to be desired but I shed about 1600 lbs with the kit.
If funds were unlimited it would be easier, so I am looking for an oem type solution. I do not want to go too overboard until I have the thing running and shake it out. I'm leaning toward using the drum brakes to get it out and see how much brake I will need. Not to mention make sure it's the platform I want to take forward. The pro's are it looks cool, it is low weight, drive line parts are readily available and reasonable,and last but not least, I can work on it.
He also writes:
Question: I have been told that a Mark 7 8.8 rear will bolt up the same an my 89 Mustang 8.8. Is this true and is the axles wider or the same? Reason, I want to do disk brakes on the rear end, or can I mount the Mark 7 parts on the 4 bolt 8.8 set up. What rotors would I use.
What do you think would be the best cost/performance option

Yes, the Mark 7 8.8 rear end will bolt up or you can swap the Mark 7 rear disc brake setup/side axles to your mustang's 8.8.
In both cases however you would be using the Mark 7 side axles and they are indeed wider than the stock mustang side axles. This is a very common swap but while they will bolt in, you may have clearance problems depending on what wheel/tire combination you run. I have them installed in my 92 ragtop and found I had to roll the rear fender lips in order for my tires to clear. No big deal really, you just need to be aware of it.

[Julian]

I have install a 85 mark vii diff on to my 90lx, how or where do measure my off set,

[tripleblack]

One offset that is involved is whatever is built into your wheels. This has a lot to do with how much clearance you have. Measuring offset on wheels can be tricky, but you can often find out what it is simply by checking with the manufacturer's website.

These are good instructions for measuring wheel offset:

http://www.ask.com/bar?q=how+to+meas...ech-wheel.html

[Julian]

thanks for the info, now i have the right wheels, I now need to replace the master cylinder, I used 96 front brake system and 85 mark 7 rear diff disc brake system, does any one no what MC do i have to used?

[tripleblack]

What year Mustang is it? 1996 GT?

[Julian]

front brakes system are from a 96Gt, (yes) and rear are from 85 mark 7 disc brakes (installed complete diff)

[tripleblack]

OK, I'll try again, is the car a Mustang, and if so what year? If its NOT a Mustang, that's OK, but without knowing what car the two different brake systems are sitting in, we have no idea of the current braking system, ie, master cylinder, brake booster, plumbing or brake balancing /valves, etc.

Your question concerning which master cylinder would work has a lot to do with what car it works in.

Assuming you are talking overall about a 1996 Mustang GT, the existing master cylinder and proportioning valve should work.

[Julian]

1990 mustang lx i have the stock mc and booster, i in stall 96gt front brake system and 85 mark 7 rear diff with disc brakes

[tripleblack]

I would stick with the stock master cylinder and booster for that GT. Updating to a newer model mc could also be done, but with the newer Mustangs and Lincolns you are looking at a hydraulic booster that works from the power steering, while the older Mustangs used vacuum boosters.

[Julian]

Thanks for the info.