Not a middy but SWB, this was the original layout, sizing it around some commonly available plastic bins made it an easy build & it worked great. I was lucky to have some waterproof HDF panels to build it with, not sure how easy that stuff is to find now.
Recovery gear storage & a cheap thermoelectric cooler built into the front.
Then the 2017 rebuild when I installed a proper fridge:
Deep cycle AGM battery sits in where the old cooler was:
1988 BJ74. The box is a Weatherguard "PACK RAT" model 308-3 48Lx39.75Wx9.5H. They now offer one that's 4 inches taller and I would have opted for that if it existed when I got this one. 338-5 | Pull Out Storage | WEATHER GUARD
It's heavy, really heavy, but damn tough. And, it fits the truck floor dimensions like it was custom-built. Not cheap, not custom, but very acceptable in my view.
Note the drawer handle was added by myself as the supplied handle would have interfered with the rear doors closing.