Xactly right Mike.....
Although the T5 is made by Tremec it is usually referred to as a T5 because it was originally made by BW. I cant see the front face of yours to see what the cluster bearing retainer is so I cant say if it's a WC version or not. see here to identify:
http://www.5speeds.com/t5/
And Mike is once again right with his assessment of the 3550/TKO's etc. Good solid transmissions which will stand up to a lot of abuse.
Later versions of the Tremec are known as the TK500 and TK600 as mentioned earlier.
http://www.fortesparts.com/tremec.cfm
Higher torque again and much better ratios.