Classic/Antique Car Repair: 1968 For f-100 fuel pressure problem, back pressure regulator, street dominator

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
As for venting, there are 2 hoses on your filler tube to your tank. The 2" and a 1/2".  Put a tee in the 1/2" and run it out to a vent location with a filter on it.

They also make a fuel back pressure regulator that goes inline and is adjustable. I had to put one on a 3-2 barrel setup before I could ever keep it from flooding.