If the blades are open enough to expose the ported vacuum hole and the entire transfer slot, the fuel is dripping from the boosters because the main circuit has been activated(from the blades being open too far).
Simply put, the carb lacks the idle circuit capacity to supply adequate fuel flow with the low vacuum signal.
There is nothing “wrong” with the carb...... it’s just not a good match for the application.
If the cam was 10-15* less duration(resulting in more vacuum), the carb would work just fine.