Well I have an all factory steel ‘74 Dart Sport that has wide lip quarters so did my rusty ‘70 Duster that puzzles me,Did the aftermarket quarters have an even wider lip?
Yes, they have even wider lip. At least on the earlier cars. Not sure about '74.
These were the quarters offered before AMD.
That's just one quick clue. Then look at the inside the 1/4 from the trunk and look of a factory like pattern for the spray on undercoating. And then look at how the bottom of 1/4 is connected to the trunk floor extensions. Factory was spot welded.... on and on.