If you look in the tech archives you'll see a couple of articles that I wrote for Mopar Muscle magazine on a 427 inch small block that we built last year. We used Edelbrock heads with the Stage III porting. Those heads will easily support 550+ hp. That 427 made a little over 500 hp with a super small cam and carb. It isn't a drag race motor so we didn't put a big cam or a big carb on it.