Given the generous cab width of your PU finding a seat should be pretty easy. I would think most Fords up to at least 74 would be candidates.
Finding a seat for a '46 was hard. Finally sectioned 4 in. out of a Mitsubishi PU seat frame so it would fit in the narrow cab, and reupholstered. Used cutdown seatfoam from a Chrysler mini van third row seat for the base. Also had to redo the latching geometry because the seat laid too far back for the cab.
Reupholstering doesnt have to be real expensive depending upon your objectives. I think mine cost $150, material and labor. But it was done by an experienced man at his home upholstering shop (no overhead to pay out).
Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.