Auto Racing: 68 f-100, street dominator, vent line

Question
i have a 1968 for f-100 with a 302 motor in it. the motor has electronic ignition, headers, holly  street dominator intake, and holly 600 cfm double pumper. the prooblem is that the gas tamk is holding an extreme amount of prressure that is flooding the carb out and yesterday i went to open the gas cap and it shot the gas cap and fuel 7 feet from the car. i was told to try a vented gas cap but have been unable to locate one, and someone suggested drilling a hole in the gas cap but it is external. what would you suggest?

Answer
I don't understand how the tank is building pressure. Does it have a in tank electric pump?
Sounds to me like you are missing/plugged up the stock tank vent line.
I would either pull the tank out or inspect it real good from any angle you can to see if the factory vent is working.