yup i went thru alot of fenders to get the one i needed the marker light hole on my 72 is above the body line in the front and the darts are below and much bigger and the point is about a 1/4 inch longer
I just searched for some Dart/demon pics on the internet. They are definetly the same.
Now there is a difference between 70/71 and 72 fenders. The marker lights are larger and recessed into the fender in 70/71 - it's below the body line. In 72, they went with the universal lens that they all had, and it IS mounted abouve the body line. Are you sure you're not comparing different years?
No to mention, I know the doors and hood are also the same for both vehicles, so the fenders would be the same where they all meet up too.