I had a similar set up in an 83 El Camino, basic stock 350 shortblock with dished pistons but had the Vortec head kit on it. Had a Performer RPM intake and a Speed Demon 750 double pumper(Holley 4150 carb but better) and a decent cam. You can get the vortecs made for higher lift cams now, when I bought mine I couldnt go higher than a .470 lift. Even with the milder cam it had a nice lope to it and had plenty of balls. If you go with the Vortecs and the cam, get a better intake, at leasst the Performer RPM with its raised runners and a bigger carb. 500 CFM is too small for a built 350 with a bigger cam and headers. A 650 would be a decent size. I never had a lot of luck with the Edelbrocks(Carter clones), they would run great but would heat soak and puke gas out the vents on a hot engine and flood it out. Be hard to satrt after sitting a little bit on a hot engine. I had to use a heat sheild/spacer to solve that problem. Always had the best luck with the Holley 4150 carb, mainly the double pumpers. The Q jets in tuned form are good to and have tha cool sound when the hge secondaries open up, lol. I had a 72 C20 also with a 350 and three on the tree. Was a nice truck and did the intake and carb on it along with a conversion to a racing HEI set up.