I searched for commercially made wheel well tool boxes but couldn't find one that I liked. It seems most of them are designed for trucks without toppers. I won't need to get into mine on a regular basis but it will be nice to always have various things with me (ballmounts, ratchet straps, torque wrench, etc.) The closes one I could find that would have worked for me is the Swing Case. It gets good reviews but there were two things I didn't like about it: Having to drill into the truck bed to mount it and having to remove the rear tie-down anchors. So I decided to weld up my own. They do not extend beyond the wheel well so I can still slide a full 4' x 8' sheet of plywood into the bed. They are custom designed to fit into the groves of the bed, and are secured from tipping over by bolting to the deck rail. The finish is Rustoleum bedliner from a rattle can. The top of each has a tray which will be useful for setting stuff on those occasions where I camp in the back of the truck.
Left side:
Right side:
Right side, top open:
Right side, bottom open:
One benefit: Before this I had to keep several bags of kitty litter in the truck to get the back to squat enough to fit in my garage due to a soffit that hangs pretty low in the garage. With the tool boxes in place, and one of them already full of stuff, I was able to remove the ballast.
Left side:

Right side:

Right side, top open:

Right side, bottom open:

One benefit: Before this I had to keep several bags of kitty litter in the truck to get the back to squat enough to fit in my garage due to a soffit that hangs pretty low in the garage. With the tool boxes in place, and one of them already full of stuff, I was able to remove the ballast.