If the TC was equiped with a 5 spd. it has 3.55 gears, if it was an automatic, it had 3.73's. Both are equiped with a limited slip diff.
The housing is a direct swap into a 79-93 mustang, but there are a few differences. The TC rear is in deed 1.5" wider (measured from axle flange to axle flange) but the houseing itself is the same width as a mustangs. The extra width comes from wider axels to accomodate the ABS exciter rings.
If you have an 87-93 mustang you will need a 79-86 master cylinder to provide the extra fluid volume the disks need. You will also need to gut the proportioning valve for proper operation (or buy an adjustable valve). You will also need to get 93 cobra parking brake cables (the TC's are too long). The rear disks have a threaded piston that threads out slightly every time you use the parking brake. This is how the rear disks maintane proper adjustment. If you don't use the parking brake the rear brakes will eventually stop working. (not good)
All in all it is an excellent swap, that is tons cheaper than aftermarket rear disk kits.
