I did some 90 metal bracketry like you'd use on a wooden deck
3 screws into the side of the drawer, 1 5/8" bolt through the wheel well. You could epoxy the bolt in, I imagine, to make it even easier to spin a nut on/off for quicker removal- but it is pretty easy to get a wrench on the bolt in the wheel well, and reach in with your hand to the nut.
I do use a dab of silicone to keep water from seeping in.
Then run a few screws through the floor of the box into where the metal carpet lip is at the tailgate. Should be plenty to hold things together and it only takes a little while to pull it all apart
3 screws into the side of the drawer, 1 5/8" bolt through the wheel well. You could epoxy the bolt in, I imagine, to make it even easier to spin a nut on/off for quicker removal- but it is pretty easy to get a wrench on the bolt in the wheel well, and reach in with your hand to the nut.
I do use a dab of silicone to keep water from seeping in.
Then run a few screws through the floor of the box into where the metal carpet lip is at the tailgate. Should be plenty to hold things together and it only takes a little while to pull it all apart

They are bolted down in the front with 'T' nuts which run through the bed, and in the back they're secured with some aluminum angle bolted to the rear seat. I also plan on putting some u-channel trim around the edges of the aluminum so it won't scratch the finish of the drawers, and waxing the drawer runners. And then I'll have to buy a fridge to put in there next to them, and figure out the rest of a sleeping platform.