trunk lid
The interchange is '70-76 Dart Demon, Sport, and Duster/Twister/Feather Duster in that body style, and '70-6 Swinger, Scamp, Dart Lite, and the 4dr's in that body style. There were differences in innerstructure bracing for the early models that have a wing/spoiler option, along with the '76 aluminum versions. Also the early lids on the Duster/Demon have a different ridge appearance on the outer skin vs the later lids. They all will bolt on and fit however. Naturally, the emblems and trim can be different throughout those years too.