Leaky gas cap

[tonymus]

I recently bought a 2 owner '72 shortbed. The 2nd owner replaced the gas tank and repainted it the original color 6 years ago. It's a 350/350 with a posi rear. I love driving it with one exception- while driving, gas will spill out of the filler when the tank is full to half full. I took off the cap that came with the truck as it wasn't an original. I tried an original with no luck and even tried shimming the gasket with another thin gasket. That helped some, but not enough. Anyone else have issues with repo tanks and filler tubes? I've owned a few 67-72 trucks and never had this come up.