Good morning Greg and a big welcome to the board!
Really good '72 doors are hard to come by and your best bet is
to cruise the forums parts board and shop for one local to you.
Another option is to consider becoming a registered member so
you can post a want to buy (WTB) in the same area.
As for a door from one of the medium duty trucks, I'm not sure
but I can go look once it's daylight (have one stored here).
Looking forward to pics and, again...