Would a well ported set of heads (like Edelbrock or SM) and a well matched intake get you there? 5 hundo HP with a 318 and say, a solid roller cam with sub 230 degrees or duration?
If you are serious about making power like a late model engine you need to disabuse yourself of the notion that a Chrysler head with standard rockers is worth spending a nickel on.
If you want to build a 500 hp 318 with a small cam you use W2 heads or better.