There should be a tag on the rear section of the T-case, held in by a screw.
I'm sure yours looks nothing like this one, but
As far as attaching a T-case to a 2wd transmission, I believe that was only done on a BA 10/5. You can convert a 2wd trans to a 4wd trans, but you'd need the rear housing, and output shaft... by the time you're done, you might as well have just gotten a 4wd trans, since you need vital parts from one anyway.
The AX-5 is not a rare transmission, you shouldn't have trouble locating one at a yard.