Here is the breakdown from my years of junkyard doggin' and swapping stuff around:
The Valiant and Duster shared fenders each and every year that they were made. Dart, Demon and Dart Sport cars also fit each other. The Plymouth models and Dart models do NOT interchange. They will bolt up to the car though if the entire front clip is swapped. In simple terms, a 67 Valiant could have a 76 Dart front end on it if you so desired.
1972 Valiant/Duster fenders are NOT 100% identical to the 73 and later fenders because 1972 models had a tab near the headlight area to support the metal bracket that retains the upper portion of the grille. Otherwise, the 72-76 look the same. In late 75 or so, the RH fender was redesigned for a different antenna. The hole is slightly different but if the later antenna is used, it isn't very noticeable.
I have several in good condition with zero rust. I didn't take note of your location, But let me know if you are interested.