Well, contrary to popular belief, the 944 could be had for as little as $3000 for a smooth runner. My friend got his for $2000. Yah you might as well scrap the 928 idea, I heard those V8's are impossible. Perhaps you meant 924, which would be the predecessor to the 944, good handling so it would make a track car. Also, if you could get an '81 924, its over 25 years old, no more emissions nazis to worry about. Only thing with those Porsches, parts may be a little pricey, and making a drag car of it will be expensive, the NA versions run high 15's/low 16's i believe. A 944 turbo could be had for $7000 and up probably, that would solve both problems.
If you are money limited, no way you can work on an E36 M3. Too expensive. German tuning is already expensive, and if you're paying >$10,000 just for the car in stock form, you're gonna be eating ramen noodles for a looong time.
Dunno how well a Camaro will handle a road course or AutoX course....not to be biased, but they REALLY aren't known for their pristine handling...
I agree with Redneck383, FC RX-7. Get the TII since you want power, you get great handling since the motor is mounted farther back in the chassis, and it would be unique and fun.