383 for a 67 cuda
If you're looking for 500 hp out of a 383..on pump gas..., those heads ain't gettin' ya there. Better consider Eddy's or Indy's, etc.
You'll need more than heads to get 500+
You'd better consult an EXPERIENCED engine builder. This build is NOT for a newbie! You can't just throw a bunch of parts together that your buddies tell you.