Big horsepower 318 builds

Hysteric said
Had a chat to a friend of mine who built a 290 ci 273 (large over bore) with ported 273 stock heads and a big solid roller with webbers that went into a local circuit racer that he says made 458 HP @ 6500 Yes that's 6500!

That's 1.57 HP per CI.

That's nice.
But we're looking for 500 HP with a teeny weeny bore and a short stroke.
Where will we find 50 HP in the same rpm range