Edelbrock models 1405 versus 1406 carburetors
Hey Billy.
I noticed you haven't mentioned anything about playing with the air valve door weight or the attack angle of the blades.
These would be the 1st and 2nd places i would begin to play with to get the smooth transition from the primaries to secondaries.
Also you can drill and tap the air bleeds to accept holley style air bleeds making it easier to try different calibrations to see what your motor likes. My understanding of the edelbrock carbs is that they are a chev generic calibration and so need work to suit other engines.
I would look at working with the original design ie changing ifr's and iab's sizes before starting to drill any new holes and change the original design parameters.
You can also find old 625 carters from the pre Federal Mogul era and study the calibration of the carbs and compare to yours and swap boosters out and so forth. When you look at the earlier carbs you'll understand what i'm talking about.
Hysteric