I see the piece you're talking about. The new one is probably missing it because it is not part of the stamping, but a factory spot welded on piece. You might need it on your car. Sometimes aftermarket parts are not very good. I'd stick with good factory pieces whenever you can. I think 67-76 Darts & 70-76 Dusters used the same rear splash shields. (Keeps water & road debris off the door hinges & helps keep noise down in the interior) I could be wrong though. You will get the correct answer here.