Instead of reducing the fuel flow to improve A/F ratio why not increase the airflow with something like a ...TURBO!
...just kidding plus I know little or nothing about big V8's other than some crazy guy named Yenko crammed 427's into poor little Camaros.
Maybe the throttle linkage is not set right and just opens the carb too much for the throttle position/rpm/actual airflow. I can't think of what other parameter a car that old would use to decide how much fuel to pump ...pump... maybe fuel pump related?
Edelbrock folks usually seem like nice, friendly, helpful. Did you try calling them?