I am contemplating getting one of those side units from Lowe's. They are made to sit on the top of the side rail of the bed. But what I may do is mount it in the bed, up against the front of the bed or near the cab. Now, I have also taken notice that the lid will have issues opening, well that is what they make uni-strut for, you can get it in either aluminum or galvanized steel, I think even stainless-steel. The only draw back I foresee is the fact that box isn't that big. But, if a person is really in need of that much storage then a tonneau cover might be an issue as well. If you want to go to a Lowe's website then here is the information
Item # 693646 Model # 63214868
I'd post a link, but fear violating a rule or something.
I am just looking for something that will incorporate my tonneau cover, still allow me to get the most use out of my bed when necessary and be able to stuff my ratchet straps and junk away, not inside the cab, and maybe occasionally haul a long rifle or 2. Maybe my post will help, maybe not.......Oh, you can get uni-strut at just about any electric supply house, most carry it in 10' lengths, slotted or plane.
I don't think you're violating any rules posting a link in a forum. Here it is: