Are you sure the fuel is making it from the pump to the carb? It took me almost 6 months to find a small peice of crud lodged between the fuel filter and the carb inlet port. I replaced just about everything else before I found it. It would let the carb idle ok, but cough and backfire under acceleration (on a hill in my case). I replaced the fuel pump, fuel filter, rebuilt the carb, new float, and adjusted the float before I found the culprit. Could be causing your problems.
Good Luck!
Marc in SF
63 Comet
Dual Cupholders