damn gas all over the side of the truck? any cures?

[67cst]

hey guys whenever i fill the tank in the 71 i get gas on the side of the truck, do i need a new cap with a better seal or is this just normal, the paint on the truck sucks anyways so i dont care too much but oneday when i paint it id love to have that problem taken care of, any i dont want to just fill the tank half way or id be at the gas station everyday

thanks, Derek