not sure as to what you mean by a little extra cash. but you will soon find out that 500hp doesn't come from a little extra cash. i have a 87' camaro that i have already completed and they dont handle that kind of power without a lot of modification. with that kind of power you are going to snap those small 7.5" ring and pinion gears in a hurry, i know i did within the first 3 weeks i had my motor in. then i ended spending 3200.00 on a 12bolt moser rear for the car. not to mention that the factory 700r4 can't handle that kind of power either. i ended up going with Monster transmissions for a beefed up 700r4 (1400.00+400 for the stall), but when you take the 3.06 first gear and the 4.10's i have in the car, first gear was kinda a pain in the butt. since then i have replaced it with a ATI th350 with upgraded 2.75 first gear. then you will also have to weld the subframe together otherwise you will twist the body, you will also have to change the radiator and fan as the factory one sucks. i would say that i ended up having around 8000.00 into things other than the motor, just to have the car handle 500+hp.
currently i'm running a 561hp/527tq 385cid, and i would say between the motor, trans, and car i have between 16,000-18,000 into it.
just to give you an idea