73 VS 74 Duster Front Bumper Differences.

That's interesting stuff there!

My car is a St. Louis, MO built car, but it doesn't sound like that matters. The fact that yours doesn't have the captured nuts for the non-shock mount brackets is a pretty good indication it came that way, although I suppose anything is possible. Mine has captured nuts in both locations, so either bumper can be mounted.

The November build on your car matching with the interchange listing for the '74 bumper listed by the OP above makes me think you're right about the shock bumpers. Early '74 cars (August to November) got the '73 bumpers as described by the interchange. The changeover happened in November, but some kind of issue came up and they went back to the standard brackets, only, they had already made the assembly line changes on the bolt locations on the bumpers, or for some reason it was easier to change the brackets than change the bumpers back. And the rest of the '74 cars got non-shock brackets but with the "new" outer bumper.

I wonder if they intended to retro-fit the later '74 cars with the shock mounts when they were ready? If that's why they installed the nuts for the shock mounts on the later cars even though they sent them out with non-shock mount brackets? Or why they changed the mounting brackets instead of just moving the bolt holes and using the old style brackets?

Ma Mopar never fails to entertain. :D