I've never seen a 2 bolt make anywhere the same power a 4 bolt will. It's to do with the fact there are only 2 bolts holding the head on, they warp even without running high compression. The only thing good about a 2 bolt is they're cheap to practice porting technique and doing boost ports for case and bolt on reed porting. If you want to learn about porting feel free to send me a pm, I'll gladly share the improve learned these last few years building them.
Justin