It seems like Amerigo
went to the flat slab door around '76 or '77, I'm guessing fit and sealing issues of the fiberglass door prompted that change.
Here's a pic of the later year one (not mine).
You may be able to find a generic slab door from an RV supply store that's close in size & build a frame for it from aluminum angle, lightweight would be the main goal I'd think.
I know you can't save everything but I'd hang onto the hinges, door latch & window if you don't reuse them......I'm sure there's an Amerigo
owner out there that can use them!