I would urge you to consider building a 383. You could easily get 500 hp at the crank, and still have a street friendly vehicle. But if you want 500 whp, then I would seriously consider adding a 100-150 shot of spray. It is the most economical way to get the hp you are looking for while maintaining a car that is fun to drive on the street. Check out the 503 hp 383 build here:

www.airflowresearch.com/chevy_dyno.php