Of idle stumble, Holley 4010

Probably time to work the primary squirters & primary cam positions. What's your initial/ total timing at 3000 rpm? Optimum is 12-16 BTDC at idle speed, 34-38 at 3000-3500 ... You probably will need to add more initial, modify the distributior breaker plate to limit the mechanical spring & weight advance. I would do the timing curve(FIRST!),before touching the distributior.