[hedonite]

There's a 7.5 on e-bay today for a t-bird

 

[M&M CUSTOM]

For the T-bird I would hold out for the 8.8 inch.

 

[tbirdscott]

You need to look for one out of an 87-88 turbo coupe, they had the 8.8" posi, the earlier tc had the 7.5"posi and the other models had the non-posi 7.5" should be the same with the cougars, the XR7 should have the 8.8"

 

[M&M CUSTOM]

According to an internet search, T-birds had the following axles for the years stated.

57-79 came with the 9 inch.
80-86 came with the 7.5 inch.
87 came with either the 7.5 or 8.8 inch.
88-95 came with the 8.8 inch.

 

[jimfulco]

'83-'88 V8 & V6 T-bird's came with 7.5's. Some of the V6's had 3.27 gears. V8 cars usually had 2.73's. The '87-'88 Turbo Coupes had 8.8's with rear disc brakes & either 3.55 or 3.73 gears w/Traction Lock. Earlier TC's had 7.5's with 3.45 gears w/Traction Lock.