looking at putting a cam in my 77 . running into same issues . according to J&P Cycles tech staff - depends on whether you have a ring around the face of your cam ( have to check with them again to verify but , if you have a ring it's a late 77 , no ring equals early ) . early / late only matters as far a cam is concerned , everything else doesn't matter . and , the only way to find out is to look at the cam . no numbers , letters , or dates can help . haven't posted question on the horse's board yet but that would be my next stop .