Most any of them will require some modification for mounting. But making a bracket to fit the cab mouting points is pretty simple (I used the OEM sliding base from the truck and added a bracket to mount the seat).
There are a lot of options. Look to minivans, etc.
I went with Pacifica rear seats. They were take outs from a new van a couple had converted to wheelchair access.
I paid $50 each locally on FB market (and local means you won't have to pay shipping).
Bonus that they are heated.
My rule of thumb was to keep the seat the same height as the OEM S&S seats. any taller and people with short legs will just dangle uncomfortably.
Local junk yards will have tons of good seats, too.