If you think the carb is too small, put a 1" square hole spacer underneath it.
The sputter could be a fuel delivery issue as well. If you are draining the bowls it will certainly lean out. Check your fuel pressure.
Since you indicate the idle screws are "way out" as well, start with the basics. Check the float settings. A low fuel level will lean out quick when you jump on it.
Re-jetting & tuning that carb is simple enough. You can download the manual from the edelbrock website.
B.