75 dart sport front bumper interchange

The 1973 Duster front bumper was a ONE year design, as far as I've been able to tell.
The 1974 models look similar but they had a thick reinforcement bar behind the bumper. Some 1974 models and all 1975-76s had that shock absorber bracket to comply with federal regulations. No 1973 models had the shock absorber type mounts. The threaded holes in the frame rail are different for each design too.