For stock 88 TC with 5 speed/3.55's?
Have 3.55's and a tc t5 in my mustang, and /i need to get the correct gear!
I did find the answer via google. For a search later on if someone needs. The 88 Turbo Coupe uses a white 17 Tooth Speedometer gear
The online calculators need tire information as well. A good one to use is here:
http://home.mchsi.com/~jroal/drive.htm
Darren