I have a 74 Duster and am wondering what year model fenders will work and what is different about them. I was looking at the AMD catalog online and they are showing 72-74 Duster Fenders as the same, but Dart fenders as having a different part number. Obviously they need to be 72-up fenders because of the side marker lights. Several people have various year and model fenders for sale around here and I don't want to waste money buying the wrong ones. Will 76 Duster fenders work? What about 73-75 Dart Fenders? The body lines all look similar. Thanks in advance

No Dart or early Duster fenders will work UNLESS you use the entire front clip. With Duster fenders the rear dogleg comes pretty much straight down while Dart fenders come back at an angle, that is the biggest difference. I don't believe you can use 72 fenders either becasue of the way the grille and core support tie bolt on, but I might be wrong. Any 73-76 Duster or Valiant should be the same.

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.

So it looks like 73-76 Duster/Valiant Fenders are what I need to look for. I think I have some here locally I can get, I just wanted to be sure so as to not buy the wrong ones. Thanks for the help!!!

Lucky for you, the ones that you need are also the easiest to find.
Cool deal.