cam plays a lot to do with the hp but the heads do to for rpm hp and torque iron gm s 781 or edebrock rpm s heads edl-60459 will work to build for torque will it make 500 hp yes and 12to1 can be done i ran a 14.5 548 big block on the street with a 748 lift cam with 278 at 0.50 on a108 it was like a chain saw i ran races gas in it but it was one hell of a ride never had no trouble with it no bs i ran it for three summers and sold it to a guy who put it in a tub out model A roadster for the street very very bad