1972 Scamp to 1970-71 Dart Marker light conversion?

Your best bet is to cut some from some junk fenders. The marker light area is usually ok as far as rust goes so im sure there are some rusty fenders out there that would donate them.
Front and rear should be the same size.
You might want to check the location of the 72 marker light compared to the earlier ones. I think they are in a slightly different location so the original hole may need to be patched if you want to be totally correct.