What about the newer twin turbo motors. I have seen a bunch on ebay selling for $899. A few came with a auto trans.
twin turbo motors: 1jz-gte or 2jz-gte, very similar motors, one is 2.5L, the other 3.0L. the one on ebay you saw was probably a 1jz-gte (a very cheap one i might add... unless it was a 1g-gte, in which case, it might not be worth swapping in-- that motor is a very old 2 liter twin turbo i-6).
look at the threads in the 1/2jz section under 'turbo talk.' the 5spd in your car won't bolt up to the 1/2jz without a bellhousing from a 5spd 92-97 lexus sc300 or a 5spd mk4 supra n/a. another option would be to fit an r154 transmission in from a mk3t. you would need a bellhousing from a non-us market mk3 supra that had the 1jz in it, but the r154 handles high power better than does the w58 transmission in your car. there's a thread about the r154 in the drivetrain section.
anyways, look through the threads in the 1/2jz section, and go to www.norbie.net
. the 1jz swap should be very similar to the 2jz thread.
search-- all of this has been covered in depth before.