[blykins]

I'm building a 427 2x4 LR road race motor right now. I've had to order another set of custom slugs so this build keeps dragging on....

Regardless, the factory LR manifold isn't exactly a slouch and we've got about 285 cfm out of a set of C3 LR heads, up from about 240 cfm.

A head and cam change would really turn that engine on. If you like factory iron, your heads can be worked. Otherwise it may be more cost effective to go with a set of edelbrocks. Even out of the box edels with a nice valve job and backcut valves would be a noticeable improvement.