My truck was a little older, but the step side beds look about the same. My truck has the correct 48-52 fenders, the 53 on up used the larger fenders.
A step side bed is really easy to build from scratch, and you can put the fenders anyplace you want/need to.

I used 18 gauge flat steel, added a 45 degree bend at the top (modern trucks have a 90 degree angle), and then added a 1" conduit tube at the end of the 45 angle. The "stake pockets" are 1 1/2" square tubing added 1/2" in from each end. The early step side stake pockets were pretty stylish, but after about 1060, the stake pockets were square channels with flanges spot welded on. Its your option if you want to cut the pocket opening in the angle piece. Inside the bed sides I welded a 1/8" x 1 1/4 angle front to back at the floor height. The bed sides bolt (or can be welded) to the bed floor through this angle. If you really feel ambitious, you can bead roll a design into the bed sides and even the bed front. I made my bed sides a little short so I could add a piece on the bottom like the original trucks had. I also built the running boards for the bed and the cab.

The bed front is also flat 18 gauge. I added a 1" wide 90 degree angle on both sides where they will bolt to the bed sides.

I also made a tailgate with square tube and expanded metal. Gene