Good eye Bill! As you saw, my linkage is not progressive. All four primaries open at the same time. This wasn’t necessarily done on purpose. This was the linkage I got with the original 427 so I used it. I do have progressive linkage available but the engine seems to respond well to all four barrels opening so I left the linkage in place.
Any reason I should re-consider the progressive linkage? I would guess mileage would be better since just two barrels would open at first.