Can you change vent and filler tube

Does your filler tube just screw to the inside of the quarter panel with the gasket inside. I was wondering what keeps it from leaking.

Leaking at the quarter panel? The gas cap keeps it from leaking.

72 SwingerJosh do you mean water leaking into the trunk? There is a gasket between the filler flange and the body and the filler tube installs from the inside not the outside so the filler flange is inside the trunk.