Please help info needed 67 dart gas cap!

Thanks everyone for the replies. I guess the question I have now is am I ok to use a cap without pressure release. I hear horror stories about the gas tank collapsing or expanding due to pressure issues. From what I am gathering even in my 67 dart there was a way that the tank was vented to release the pressure. If so where would it be on my tank?

Carl

some 70 cars and everything 69 and earlier had unvented caps, no pressure relief, no nothing. completely sealed. as above vent line came off the filler neck. look in your trunk, feel your hand up high on th efiller tube