I found this pair at a semi-local GM dealer (this is not the same set that was on eBay recently). I was told these parts were discontinued in 1983. Part numbers are as follows:
- Driver's Side: 3962531
- Passenger's Side: 3962532
They are both gray fiberglass (I don't know why the driver's side is black on top). To use them as is requires cutting the entire door frame off. If a person wanted to retain the vent window, these door window opening caps could be trimmed accordingly.
I sacrificed an old door with issues to take the pictures due to these requests:
Enjoy!