Holley carb jetting 101

The 670 should feel right at home on that setup. I'm running the same carb and it was great right ootb. The only problem I had was just like you I turned the mixture too low causing a lean condition that made it surge and hiccup when driving. As far as the plating falling off, I think that is just on the older models and Holley replaced one members carb no questions asked once he contacted them.