Duster sheetmetal interchangability

A couple of differences that I can think of. The doors changed in '73 to the style you now have. The interiors changed, but you asked about sheet metal.
As to the tail panel, in '72 the trunk floor was straight across the back where the tail panel is welded to. The later trunk floors had an offset along that line. I used a later trunk pan and had to use about two thicknesses of body metal to fill in that gap. If you go with a Demon tail panel you will also need whatever framework is behind the panel for the tail lights to fasten to.
The Demons also had a different front end, I think it shared with the Dart and is different from the Duster.
C