Porting along with bigger valve's will help, but the overall port size will still be to small to support 7,500 rpms. You need cylinder heads that have bigger intake runners, like 170cc or 180cc. Those 273 rocker arms are probably 50+ years old and I wouldn't trust them for your application. Some on here will probably disagree with me but those rocker arms have been known to break. You'd be better off with a set of aluminum roller rockers. What intake manifold you plan on getting?
