Here are my files. Use at your own peril, but they worked well for my '84. I also show on the files where to cut the panels if you're using the 62 series rear 3-point seatbelts and factory trim cover, which is what I'm doing on my '84. I think I added a fastener in the trimmed version, so you might need to drill a hole in your inside steel for this (or delete that fastener).
Again, these files are for early trucks that do not have jack and tools stored in the side of the cargo area.
There are 2 versions, one with geometry to match the factory fasteners, and another with that geometry replaced with 3mm holes at the centre of the factory fasteners, so you can modify and use whatever fastener you prefer.
If you use these files and create new panels for your rig, please tag me so I can see what you did. It's always good to see different ideas on how to replace the tired, factory side panels. And if you find something that doesn't work with the files post up here. I'm happy to change them if something is amiss. Though as mentioned, they fit my '84 perfectly.
EDIT: May 5/23: updated to combine all versions into one file.