1973 duster rear bumper

The rear bumpers on a Duster are dimensionally identical from 1970-1973, and none of those used shock mounts.

One or more of those years has slots in the bumper for a different bumper jack attachment, but other than not being “correct” for a certain year they all interchange.

For that matter, the 67-69 Valiant rear bumpers are also dimensionally the same and will bolt on to a ‘70-73 Duster. But those have backup lights in the bumper.