that's a rebuild with some "R" series toyota parts in it most likely. Toyota made some upgrades in 96 to different helix angles and the like. I never did find out of the AX-15 got those upgrades, but they should slip into the AX case. Try contacting Marlin Crawler. He's the guy for the toyota boxes and could tell you what the best parts to rebuild with are.
definitely 3rd gear is the weak link. That's what fails, unless you're a full on moron, then you can strip the 1st gear cluster.
I'd slap it behind there, fill it with MT-90 and roll on, conscious that the transmission is the weak link.