Now this isn't too much help as I cannot remember the details as it was a few years ago, but I had a 318 with B43G engine. I thought the flyball was bad too. I bought a gasket kit and carb jet from boomers_influence. I will still having trouble and he told me how to test to see if it was the flyballs without taking anything apart. For the life of me I can't remember how I did it. In the end my RPM surging was the main carb jet. Looked clean but a microscopic buildup of varnish made the jet ever so slightly smaller.