I think a good plan would be to use off the shelf parts and make the side opposite the truck into an a-frame with a rope or chain connecting the bottom of the legs to keep them from splaying out.
The tricky part would be finding the proper hubs for the corners

nostr:note12qqgfz2mrx4h2l6p9qp5gmlsna5k95m335s3px97xu0p5wrfhcnqytgck0

https://i.poastcdn.org/09a9980e2d4440f1a302b5e275d6db85d0a43ca49925a9e799d5a55155329ac4.jpeg