I have to agree with Pat on this one. The stock heads are okay to 4,500 rpm or so, but they are whats really holding you back. If you just want daily light to light grunt then just swap cams and switch to carb. I bought my big block and found that it had peanut port heads too. So I found some 781's from early seventies. If you want it to be a brawler then you need heads and higher compression, cam, etc...