repinS is right in this one. A 1jz swap will cost a good chunk of change (I've seen installs with just minor issues run up over $6,000 total..). As for a 2jz, keep dreaming

There are enough issues (and costs) in installing/obtaining necessary parts (you'd need more than just the motor for either engine) that for someone new to the supra and on a decent budget, it's almost nowhere near pheasible (sp?).
Your best bet is probably to pick up a JDM 7M-GTE (I suggest
Nippon-motors.com. I (living a state away) can get them shipped to me for $900. So far, I've had good luck with them.
If you read up (on supraforums.com and supramania.com) there are whole guides on 7m-gte motor swaps. With one other person helping, we've got the removal time down to under 4 hours. My first time, it took me a full weekend, and then 4 days to remove/install, and troubleshoot several minor issues. All things said and done (when you throw things like clutch, gaskets, fluids, etc) I pulled off the entire job for less than $1100 which is much softer on the wallet than $2500.
At the same time however, You can buy a completely stock 1989 Turbo for less than $2500 if you look carefully. Then you've got more than $1,000 (if you so desired) to mod it with.
As people above me have said as well, if you put the whole $3500 into a mk3, you can find one that's already been mod'd, with a proper head gasket job, and some goodies too boot.