if memory serves, 2-bolt main blocks are good to 500+ hp and 7200 RPMs, 4-bolt main blocks are good to 650+ hp and 8000 RPMs. with a different crank, rods and pistons you can basically go as far as you want. You can bolt a supercharger on and be at ~450 hp on the stock motor I belive. I have a carbeurated 5.8L (355 cid) with almost entirely stock parts pushing out ~360. It was a really cheap build. great torque curve. There really is no replacement for displacement.