Edelbrock Air Gap on Magnum 318 Problems

Because it's a stick car, it's going to be much more sensitive to problems because the convertor isn't helping take the "edge" off any tuning issues. IMO, the 650HP is too much for the current combination. Maybe a little more gear would help it, but my impression is with the clutch engaged there's just not enough airflow at low speed. So you can mess with the accelerator pump circuits and power valves to try and get the stumble out. Or try a smaller carb. Regardless of the eventual carb choice (or EFI), some tuning is necessary.