Dart and Scamps generally do not have a vin stamped in the package tray area. That's a Demon, Duster and Dart Sport location.
On a Dart at the rear of the car, trunk lip, pass side about where the bumblebee stripe would be if it had one. Usually you have to pull up the weatherstrip.
Bingo! My car is a '73 not a 74. Now I have the giant task of getting the title corrected. I'm Kind of bummed because there were a whole lot more '73's produced than '74's.