I didn't find too many options out there for Tonneau Covers, of course a custom maker could make whatever you need.
I put a Truxedo RealTruck Lo Pro on my 72C20, which actually fit pretty good. I had to order an extra front rubber seal, which was wider, to cover the front of the bed from them. The rear over the tailgate fit well.
The problem is your stake pockets are not covered. I ended up putting some made for late model Dodge trucks that are very close to the proper size. I got some double sided sticky tape and spent the time cutting and placing it all around the edges. I was not confident that they would stay in, especially at highway speeds and these Michigan potholes
Just for info if any other members are looking at their options for Tonneau covers and stake pockets.
Tonneau:
https://realtruck.com/p/truxedo-lo-p...=1715380608433
Stake Pocket Covers:
https://www.ebay.com/itm/235110091688