Highest flowing sbm heads?

I build all my own stuff, engines, transmissions, set up my own gears and do all my own fab work. Head work and machining, I pay someone. That being said, if I was looking for a 800-1000 hp small block, I’d have it built. Just about anybody can screw together a 600 hp small block and make it live. When you are looking for another 2-400 hp you’re playing in a different league.