Unless, I missed it, you responded to everything in Rob's post #5 except the intake gaskets on the heads--did you spray around them as well. Did you spray all around the carb mounting, including the bottom. Assuming your carb is cleaned properly, valves are right, etc--I'd say you're sucking air someplace. If the problem is fuel pump related, it may be that you have a bad vacuum hose from the head to the pump. As Rob indicated, most often the pump is either operable or it's not.
I didn't intend to walk in on the party, Rob--no offense.