i measured my bed, and made a box using plywood that fits between the wheel wells. It fits the largest tote from home depot.
I put all of the hunting gear, safety, and recovery gear in the tote, and put the tote in the box. i store it in my garage on a furniture dolly. It's got a coat of black marine paint to seal the wood.
I have a milk crate and pack that sit on top, and those things go in the truck with the rifle and shotgun, load the box in the back and I am off. As i have hunted and learned, i add the things i want to carry to the tote.
I carry the tote in the box to keep everything dry, and when i get more than one or two, i take the tote out, scoop some dirt into it, and stack the coyotes in the tote to keep the blood in the tote (the dirt soaks up the blood) then when i get home i only have to clean the tote and don't have blood running down the back of the truck.
It's sturdy enough to stand on for night hunting, and have a lazy Susan shooting seat. (it's a plywood frame on a spinning base that is fitted to allow me to lock in my hunting seat into it. There are extension arms that come out between my legs that i can put the shooting sticks into. This way at night, no matter what direction I just rotate and don't have to move my shooting sticks.