With a short bed frame, your job is a whole lot easier than I thought.
There are a lot of good pics and videos on cutting the bed sides. There are also kits to shorten a frame, sold by reputable companies. Templates, plates, brake line, parking brake cables, etc. Here
I am no more skilled than the next guy but I don't consider shortening a bed side very intimidating. You just cut a section out and put is back together. Good measuring, straight angle grinder cuts and weld it. You don't disturb the header or the tailgate areas.
There will still be three stake pockets. That issue is up to the owner. Leave the center one or fill it.