This site might help. There have been a lot of t5 trans. Produced for GM, Ford, Jeep and others. Some with 1 inch input shafts for 150hp applications up to about 350hp applications. There are WC(world class) and NWC (non world class) models. Has to do with the design. The web site will explain some of it and help id the unit you have and the hp car it was designed for. If the id tag is gone, the diameter and spline count will help some in determining the original use.
http://www.5speeds.com/t5/
Richard
Memphis