Help, I need some advice, suggestions and answers..., Is this ST165 swap a good idea? Options

[tin_foil]

Okay, here's the deal. I found a kid selling a 3sgte longblock from a 1989 alltrac. (ST165) So my first question is how easily will it bolt up to my '94 GT? Will my motor mounts, tranny, ecu, etc. all work? Secondly, my biggest concern is power. I know the ST165 usually only has under 200hp, but my question is what is it exactly that makes the newer 3s so much nicer? Is it a bigger turbo? If so, this engine doesn't come with a turbo, so what if I just get a ST195, or ST205 turbine? Also, this engine is completely rebuilt and never ran. It was bored .030 over, and it has forged pistons, h beam rods, steel crank, and completely rebuilt head. How much of a difference will the bored pistons make? Can I beef this engine up to get over 300hp? Or is that just pretty much impossible with an ST165? Lastly, do you guys think it's a good deal? He's selling it for $500 which means I could probably get it for $400. I've never priced the ST165...is this a decent price?

Please give me your feedback, all. I want to call the kid back by tomorrow with an answer, so let me know what you think. Thanks...