[WSSix]

That's an easy goal to hit. I'd go cam change with supporting mods like intercooler, headers, and full exhaust and then call it done. The cam will help give it good sound which I think is important to the overall goal/attitude of a good street cruiser. It will also help you target where you want the power to an extent as well.

For reference, a stock C5 Z06 with nothing more than headers and high flow cats into the stock Ti exhaust made 540 rwhp with Pro-Charger's Stage 2 system. The Stage 2 system utilized larger intercoolers, better air intake, and slightly higher psi than a "normal" C5 kit. Given the packaging restraints on a car like the C5, I see no reason you couldn't get good intercoolers and a clean free flowing air intake into the head unit itself on a classic car with an open engine bay. Your 317 heads are basically lower compression LS6 heads.