Technical issue with my rebuilt slant six

I have a 64 Dart with a 225 freshly rebuilt. A carb I had on it before had broken causing a vacuum leak and replaced it with a fresh one. For some reason however whenever I’m idling in gear the engine begins to act like it wants to stall (kind of a violent shimmy) and will smooth out then run rough again. She also feels like she’s starving for fuel occasionally off the line. Any ideas?