I know most people like things nice and centered, but I wanted some length (full 6') in my bed, and some long storage as well. I had a custom steel box made, 24" wide, 50" long, as tall as the top of the bed, positioned on the passenger side. Secured down of course, but with some quick releases hidden inside. Just stand at the side of the truck, unlock and lift the lid and there is all is. Mostly road trouble stuff inside, tools and such. Nice place to stash guns and fishing rods.
Was reading another thread about Taco-tilt. This idea might help.
I'll get a pic up when I can.