I think you will find that the carbs in post #73 have smaller secondary t/bores & venturiis than the 625 & 750 AFBs that came with 1 11/16" & 1 9/16" respectively. They are probably about 450-500 cfm.
That's kind of an issue for sure. There weren't just "one or two" styles of older Carter four barrel carburetors, there were MANY, so it's tough to know what they all are.
