The ID of ALL B/W and Tremec transmissions is found on a metal tag bolted to the main case.
The number found on the main case or tail shaft housing will not ID the transmission.


If the ID tag is missing, is there a way to figure out what T5 I have?

Yes, there are several ways to narrow down the ID. First is to check the shifter location. Mustang shifters are almost at the end of the tail shaft housing. Camaro shifters are right about the tail shaft bushing. Second is the input shaft size and splines, third is the date code on the main case and or top cover. GM T-5 have a 26-spline input shaft where the Fords are 10 spline. The V8 Ford T-5 have a .670” pilot bearing, whereas, the 4-cylinder pilot is .590”. Fourth is the lower cluster bearing just under the front bearing retainer. Is it stamped steel or a molded bearing race? Stamped steel tells you it is a NWC where the molded race makes it a WC T5
World Class & Non World Class T5
(the name Timken can be read on the face). If Timken appears it is a WC.

This is true for all T5 transmissions.