Finding a 2.8L engine shouldn't be too hard, expect to pay at least a couple thousand dollars for it. But the hardest part will be doing the OBD1 conversion for that engine to work on 95 or older cars.
Your cheapest bet is to buy a 325 and just mod it (intake, exhaust, cams, etc etc.) , maybe do a 2.9L conversion, or just save up and buy an M3 engine.
"Driving is like a narcotic, an addiction that can take over lives. It ruins people, breaks families apart, and even kills. Itís habit that needs to be fueled. Time, money, rationality, sweat, knuckle skin, and anyone who disapproves are of little importance to a driver, and are often overlooked. Hi, Iím Nelson, and Iím a drivaholic."