You wont find a fox mustang with disk brakes unless its an SVO, or Saleen, or Cobra and the saleen unit is that same as the MK VII, however these are all 5 lug. You can also look for T bird Turbocoupe which had 4 lug, but was still wider than a fox 8.8 by 1.5" total. They can hold up o a decent amount of power depending if your using slicks, because those will cause axels to snap like a pretzel. And the average price is about 200.00 for a disk to disk rear end.