Search the Celica Alltrac forums for an ST185 transmission - they should be almost free ($50+shipping or so). Most of the other parts you can take off any gen2 with a manual transmission (cables, hydraulics, etc). You will have to drill some holes in the firewall and do a bit of wiring for the clutch start circuit, etc. You will have to get V6 manual shift cables or run a small spacer to get the shift cables to work on the transmission end. Try to get all three mount brackets with the transmission along with the clutch slave and lines. Your stock front and rear rubber isolators will work and you may need to buy an upper transmission mount.
I haven't figured out the axles yet, but I'm pretty sure ST165/ST185 complete axles will work. You should be able to find those on the Alltrac forums also. There is a small chance your auto axles will work on at least one side.
Total cost of the project should be in the $500+ range for parts, depending on the deals you get... I hope you are pretty good with a wrench too.
-Charlie