Gas Cap

I bought a gas cap off of ebay for my 1972 Dodge Dart Swinger with a 318 engine. They gas cap does not fit, the locking tabs are wider than the slots on the mouth of the gas tank. The seller stated in his listing that this is a non vented cap and fit 1972 Dodge Darts. But when I inquire why the cap did not fit he said that my car needs a vented cap.

Question, did the Dodge make 1972 Dart and different gas tanks that require a vent or non-vent gas cap?