mapax5

for your displacement, a T3 would be ideal, however, you can make do with a T28, depending on how much boost you wanna run.
also, your red-line would help too.
too big a turbo would kick in as you're red-lining (given like 6k for redline) and too small would be starved up top (early kick in, say 2.5 but die off at 5k) so i'd need more info. intercooler size is not so much important as efficiency. fitting the biggest intercooler you can fit is not smart. you have to find turbo size/spool up info first. otherwise you'll get too big an intercooler and lose 1 lb of boost, which depending on how big your turbo is, would mean much higher int. temps.
if you've never done this before, i'd recommend a shop, not offending you, but there are A LOT of factors to calculate for when going turbo. you can't just slap one on and drive.
well, you can, just how long your engine will last is the Q.
Oh, also, what kind of tuning are you gonna run?
added boost means added fuel... how you gonna accomplish that? getting bigger injectors isn't the answer either, as your ECU can only go up like 10% higher.

in a nut shell...
find turbo, intercooler, tuning for ECU, figure out about your timing and fuel, how much will your tranny hold up to, axles, also i'd check in club3800.com, they're not made for your car per say, but they do a lot of performance on grand ams, they might help you much better.
Have you thought about getting a GTP? or a V6? i've seen V6 pontiacs, and they're fairly easy to boost.
just my 5cent.