[mike16]

there are also some re-enforcing rods that extend from several fasteners on the side of the bed to the outer edges of the fender one in the front. one over the wheel arch and on at the rear of the wheel opening. three per side and maybe a forth one at the rear corner.

I believe they are the same for at least all 60-66 step side fendered trucks. If they are bent they can give your fender a saggy look. if they are missing....ditto. I believe the 60 and later ones interchange and are reproduced. it does not hurt to go through with new hardware and on the inside of the fender where it does not show.... add some large area washers.

Those fenders should not sag and should be sturdy enough to handle the weight of a full size adult.

I replaced my bars and added the fresh hardware and the bed becomes much sturdier all around and much less rattle and sweak. Add new wood, hardware and a bit of rubber between the bed and the frame and it gets stronger and even more quiet.

linseed oil also keeps a squeaky bed quiet