Horsepower limit for out of the box Edelbrock RPM heads

One user on here with a 10.5:1 408, TTI headers, and a comp PP284H, Air-Gap with a Quick Fuel 750 and stock out of the box Eddy's dyno'd at 507 at 6000 rpm and made 500 lb/ft from 3000 rpm on up. My opinion? 1.25 Hp/cubic inch isn't anything to complain about!