“a 750 double pumper carb with vacuum secondaries”
What brand of carburetor would that be?
Double pumper carburetors do not need vacuum secondaries.
BigBlockk
Later.....
Pardon, dual feed. It gets called a double pumper so often I just call it that myself.
The 390ci replaced the original 352 back in 2005-2006 and visually it’s identical to the original as it’s an FE block.