All Mustang 8.8 rear housings are the same length from 1986 to 2004. The axles are whats longer. 86-93 are 4x108 and same on both side axle length (1993 cobra is wider as noted above). 94-04 is 5x4.5 and i think .75" per side wider than the 4 lug. If you get a early 4 bolt rear you can swap the axles and disc brakes from a Ford 7.5 rear from the v6 Mustangs. Most v8 Mustangs came with 2.73:1, 3.08:1 and 3:27:1 gears and limited slips that can be rebuilt and made a bit stronger. The 3:27:1 you'll find more common in the 1999-2004 5 speed GT's and 1996-98 Cobras (99 and 01 Cobras are IRS). If you find a 2003-2004 Mach 1 rear it will have 3:55 gears.