408 aluminum head choice for 500Hp

RPM heads, corrected with a high quality 5-angle valve job, matching springs, gasket matched and "stage one" clean up and blending. IMO bush the lifter bores and run a solid roller. Depending on cam and top end, 500-550hp is easy on pump swill with a medium sized street roller, good pistons, and great machine work. With the hydraulic roller, you'll need to run a dished piston and cut down the chamber size to get a dynamic compression in the 8.75:1 range to survive pump fuel, and you'll be giving up upwards of 100hp.