And the other is the vapor barrier and some 3M Rope Caulk. The vapor barrier is treated paper with a wax coating on one side which faces into the inner door and then the bottom edge tucks into a slot on the inner door structure to direct any water back into the door to drain out the slots in the inner door structure. The rope caulk is rolled out into a bead and placed around the edge to stick the vapor barrier to the door.
Vapor barrier on my 68:
Tucked bottom edge of the vapor barrier in the slot:
Some of the factory black rope caulk still on the inner door structure:
While the vapor barrier is off, get in there and clean any old lube off things and then relube the roller channels, door latch mechanism, regulator, and pivot points.
Album of the door panels taken off when I replaced the outside door handles:
There may be die cut ones made specifically for your car and you would have to check. A better automotive upholstery shop locally to you may have the stuff in a sheet that you could cut to fit also.
The 3M rope caulk should be available from an automotive paint supplier or online. The caulk comes in a box and is in strands inside the box. I've also use the strips of caulk rolled up into a ball and then molded it around things like firewall grommets to make a better seal.
I will say I have seen plenty of door panels ruined from the vapor barrier not being in place or installed wrong.