70 duster gas filler neck.

The 4 hole neck is for a dart or scamp. and will deform the quarter if installed. The dart and scamp have a flatter quarter panel. So the necks are different. put them side by side and notice the bend difference

A 72 and up necks are different also the neck installs through the quarter and screws to the quarter. Pre 72 the quarter is screwed to the neck and the neck flange is on the inside. The indent on the quarter is different and the cap will not be flush. Believe me I have run into this problem when putting 72 quarters on a 71 car in the past. Those are my pics posted above and the differences are the reason I made those pics.

One more thing the 70 neck has a vent built in the neck. When eliminating the ecs system on a 71 it is a good reason to use a 70 neck. Also the caps fit from 67-70 are easier to find.