With the budget in mind, you'll be looking at either a T-5 or Supra gearbox. They were only made with 6 cylinders in mind. Put some fat tyres on your car and a motor with decent torque and you'll have problems. Drive it nice and they'll last forever and you'll enjoy the economy bennefits.
Usually HARD launches on these are occassional because they only let you do it once
Skinny 215 tyres will allow you to get away with more. Fat tyres and loading up your driveline will cause a "weal link" to reveal itself. ie: wheel spin releases some of the stress..........on second thoughts, not much stronger that your single rail anyway.
Here's one of the more experienced suppliers in the know - Mal Wood. You can either source your parts thru local trading posts etc or buy the whole kit thru him.
Not sure what bellhousing/clutch disc you'll need for these. Call him as if you're a customer to find out the details from going single rail to a T-5 (XF 5 speed).