My set up in the rear is a little unusual. I replaced the stock rear in my '90 GT with the rear from a '95. This had the disc brakes and 3.27 gears I wanted. I am using the '94+ wheels in the rear. The wheels are 17x9 Cobras. The tires are 275/45. I did have to pull the lip of the rear fender up. However the fenders still look original. I am still running the quad shocks, and I have no clearance issues there at all. It is possible that if I used the fox-body wheels I would have been able to leave the fender lips alone?
Don't know if this will help with your application, but it shows how you can get creative.
Good Luck.