I have my doubts it is a fuel problem. If it was fuel everyone running today,s fuel would be plagued with the same complaints. To me it could be an ignition problem or voltage loss. What starter are you running? How does it spin over? I would test the voltage at the positive side of the coil while cranking. You also should buy one of these and check the available coil output.
Tester Running stock starter, I only tested the output at the coil without cranking, and it was 10.5v, my ballast has been modified by installing a direct wire between the terminals. Like I said I've got pertonix ingnition, anyone ever hear those malfunctioning because of heat. Electronics usually don't like heat and this is in the distributor?
How would I check coil voltage while cranking, I'm not 100% .