You might be able to just move the rubber pad into a working position. Fab up a new folding leg(s) to support the seat. Use like a nutzerk into the seat bottom and screw in legs. Could be as easy as long bolts
I just recently added the later, angled long jump seats, to my 78 with factory roll bar. I bought the bracket kit from Specter. I had to drill two holes in my wheel wells, which most people wont want to do, buy my truck is just an old survivor so it didnt really matter to me. Ive had these jump seats for decades and really wanted to make them work somehow and didnt want to spend the money on short ones. The angled front end of the jump seat actually works perfect with the front bucket seats.
I purchased two collapsible boat seat legs and stuck them to the bottom of the seat for support because the rubber pads on the bottom of the jump seat dont rest on the wheel well.
I admit, this is pretty hacky, but I dont care on this truck and I kind of like the frankenstein aspect of this cruiser. Heck, I added a Sky Blue rear step to the rear bumper just because it was piece I saved off my first 40 over 30 years ago.