Random stalling while driving or coming to a stop... 340 4 spd. holley carb

Hi guys. Well after the driveshaft seperated itself from the rear end on the PA turnpike at 70 mph :angry7:, the car sat a little. We got a new U-Joint and reinstalled the driveshaft and all was well. After about an hour of driving today, the car started randomly stalling, kinda sputtering before stalling. If you kept on the gas, it would usually sputter and then run normal however. It wasn't a constant thing, rather it was intermittent but it happened probably 4 or 5 times. Any thought what might cause this? It's a 340 with a 650cfm holley carb and it's a 4 spd. The last time we timed it was during the winter, would that affect it?
The plug wires are all new and I can't see anything visually wrong with the carb, and the carb was professionally rebulit not too long ago either. Maybe a vacuum leak? It was pretty hot here today though, so maybe the fuel was vaporizing out of the carb? I don't know. any help is GREATLY appreciated.
-Jon