The .620 cam will run out of air at 5000 rpm or so with 500 cubic inches to feed. You need a lot of lift to feed 500 inches with cast iron heads. I'm not sure what the Super Stock boys run but I bet it is .750 or .800 lift and they are only feeding 440 cubes.

The easiest way to check this stuff is to buy a copy of PipeMax and plug your numbers in. PipeMax will calculate all of the airflow requirements and tell you how much lift you need given the rpm, cubic inches and valve size.

I'm not saying the .620 cam won't run great, but you'll be leaving a lot of power on the table with that small of a cam. On the flip side, you'll have plenty of torque in the 3500 to 5000 range so if you gear the car right it will pull hard down the track.