I had a similar problem on my 38 Studebaker after rebuilding the carb, fuel pump, new electric pump, plugs, plug wires, points, rotor and cap. The master wizard ( of course I mean Ed better know as edinmass) took pity on me and had me send him my distributor. Fifteen minutes later he had it fixed. It was a bad wire in the distributor. I didn’t even know there was a wire in the distributor! He sent it back it runs great, cooler by 10 degrees and 3 more miles per gallon. Follow Ed’s and Pete O’s advice and I’ll bet you will solve the problem. Good luck.
dave s
ps edit correction miles per gallon not gallons per mile ! Thanks Grony for catching it.