I've built 500+ HP 327's, but they sure didn't get 20 MPG! Our best effort on a 350 was 610 HP at 7,200 RPM with a round track engine for the Nashville, Tennessee track. It was still building torque at that speed, but the car owner didn't want to push it to 7,500 or above on the dyno.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!