Ah, the door cards: a future project for me, for which I have started to collect the bits.
All ready in my head, I am planning to broadly follow the two documented projects on Turbobricks, creating a later-style door card, including the coveted plastic door pockets, instead of the original of my 1975 car.
Sorry, but I won't partake in the plastic project.
My backing board will be 3mm plywood, as this is more resilient in my experience than masonite, can be stapled and it would hold the tee nuts to hang the door pocket on.
My LHS door card is in a better condition than the right one, and I hope it can be used as a template.
The cover has to be replaced too, as it is in tatters plus I hate the baby-poo colour. I have identified the vinyl from Spotlight to use, with a fake suede insert also from Spotlight.
The bulge/beltline Anthony mentions above will be done by combining a strip of the same ply, plus a strip of thicker self-adhesive foam from Bunnings. As in the Turbobricks projects, I will first staple the upholstery to this beltline and bolt it to the big board, so it will hold the upholstery in the middle, allowing strongly stretching it towards the edges, plus hide the stitching of the vinyl to the suede.
3-4 other under-way projects plus a long overseas trip means I may realistically not start making these this year.