*Foxchassis helped with this thread some info is from him*
If you are wondering what type of rearend or even what size it is this should help. You can find the axle code on the tag that is mounted directly on the axle housing. Another sopt is a white sticker located in the doorjamb there is either a number or letter under axle. Conventional or "open" rear ends break down as follows: 8-2.73, Y-3.08, 5-3.27, F-3.45, 6-3.73. Locking or "Traction Lok" break down as follows M-2.73, Z-3.08, E-3.27, R-3.45, W-3.73.
'79 5.0L Mustangs and Capris did not have Traction-Lok. Traction-Lok was first available in Mustangs and Capris in the '81 model year, and it was optional with the V8, not standard. It became standard with the 5.0L V8 (still optional with the 4.2L v8) starting in the '82 model year.
5.0L mustangs and Capris could not be ordered with a ratio higher than 3.27:1.
There was a 2.26:1 and a 2.47:1 ratio available with a V8 early in the Fox years.
Thunderbird Turbocoupes in '87 and '88 had an 8.8" rear, 3.55:1 with a manual transmission and 3.73:1 with an auto.
Lincoln Mark VII's came with an 8.8" rear, Traction Lok was an option
The only Mercury Cougar that came with an 8.8" rear was the XR7 models and was a Traction Lok with at least a 3.08 gear all others were 7.5"
1989 Mark VII LSC, OEM Bullitt wheels, Full coil spring conversion, B&M Shift kit, BBK Fenderwell CAI, Crane Cams Coil, Flowmaster Exhaust