Ask and you shall recieve! (Flip Top Gas cap Adapter)

I would like to know if it's the year or style....meaning we are talking Duster, so is it 72 Duster is different than 74 up Duster or 67-72 Dart different than 74 Duster...I would like to see the difference Dart Sport and Dart Swinger or just Dart.....and 72 Duster verse's Dart Sport of same year....74 Duster 74 Dart Sport.....Do we know the differences. Just wondering myself and trying to dig a little further. :)