Chevrolet factory installed carbs were Rochester, GMC used Zenith.
I don’t think my fuel pump is the problem but I have another one and am planning to pick up a pressure gauge and tee today if the auto parts store has them.
My vacuum advance works but I can manually turn the distributor to vary timing which speeds up or slows down RPM and the issue remains.
My vacuum gauge readings can’t be trusted but the needle jumps up and down in concert with the surging RPM.
