Door skin removal (72 Duster)

The door skin on my 72 Duster needs replacing. I have a good door from a 73 to use as a donor skin. The main obsticle seems to be : how to get the skin off at the top of the old door. The 73 door has a plastic piece of decorative trim that can be removed, exposing the folded lip of the skin. The 72 uses part of the inner door structure as the upper trim, (no room for the chisel). I could cut and do a butt weld at the top, but would rather not weld if I didn't have to. Anyone?
Howard