your definitely going to need a transmission to go with that, go with the 350 but do it right, if your swaping motors im guessing your trying to do the car up for some street/strip sort of performance. Get a 350 with some descent heads on it 196 or 202 if your really serious, look into crate motors, JEGS has some for descent prices, you'll pay a bit for shipping though.
Tranny you'll need something that can handle a bit of power, T350 or 400 are popular choices that can handle some abuse. 700R4 is a little weak but if you want slightly better gas milage to go with the whole package its worth looking into, you'll pay about 30% more for one over a 350 or a 400 though. Drive shaft is also something you'll probably need as well as the length will probably be different from the 2.8L's shaft.
What year is your car, and is it carbed right now? If you go with a carb you can dodge the computer stuff, you'll just need an ignition system of some sort. Marllory makes a good distributor for 350's, also you'll probably need to do a set of headers (again JEGS has tonnes) i'd recomend the "shorties" as the full length sometimes runs you into ground clearance issues, they also sell "Y" pipes to go with some sets that will save you some grief. Use the copper gaskets to by the way they last way longer then the cheap ones.
Also look into a 3" exhaust system, you'll probably need to order that as the bend over the rear passenger side axel is rather sharp and your local exhaust shop probably wont be able to bend 3" pipe without ****ing it up on ya. Flowmaster makes a great cross flow muffler with a 3" in and duel 2.5" out, mounts into the stock location.
Oh and with the tranny get a torque converter around 2500-2800 stall, its a step above stock for the V8 firebird/trans ams but it still lets you maintain day to day drivability and still have alot of go. Hope this helps.
