AFAIK all the 5.0 Stang from '85-'93 have the 3.35 1st gear(these are world class)... The non world class '83 & '84 have 2.95 1st as do the aftermarket/Ford(T5Z) boxes... Here's a list of the different models... http://www.britishv8.org/Articles/Borg-Warner-T5-ID-Tags.htm Here's another list with just Ford units and torque ratings... http://chris66dad.tripod.com/id38.html
I meant to say it's sized for a 65/66 mustang.. this is a new housing w/ rebuilt 3rd member(all new internals) and new 11" disc brakes...