500whp is going to be un-obtainable with currently available bolt on components for a naturally aspirated application. The most we have been able to manage so far with just bolt-ons was around 450whp. Cams and head work would be the next step in that direction without going into the power adder realm. Comp is currently in development of 15+ cams that will be available near the end of December. That should put you close. But there isn't much way to get to that level with what is currently available without a power adder
have to agree I'm at 442rwhp, I'm just waiting for cams to put me to 500.