Bumpers

At least with regard to Duster and Dart Sport, I think 72 and 73 bumpers ARE the same. Perhaps different slots for the bumper jack, but the shape of the blade is the same, and I believe the mounts are the same.

I'm sure you could rig the front with some custom brackets, but it wouldn't follow the rest of the nose, and would probably look worse than the big bumper. Unless of course you want to change the entire nose, which has been done and is bolt on with the right parts.