Having a dump truck it was pretty easy. Got a large ammo can, made a frame to hang it on the dump frame under the bed, hinged the lid and the box to keep everything in one place and easy to reach. Works great and keep everything dry.
The seat in my '56 comes out in one piece, but I noticed the space under the seat would fit a couple tool rolls or a flat pouch. There's also the possibility of finding a friend that can work in canvas/duck cloth and make something to hang inside the seat back between the seat back and fuel tank. I keep a pair of gum boots back there along with a binder with my paperwork and some parts info.
1956 GMC 370 dump " 'Tater "1970 VW Volksrod "the Black Bomber"
2007 Chevy Avalanche
2020 Jeep Cherokee Trailhawk,
2005 Harley Davidson FLHTCUI
I dig all cars, old and new, whether they were hammered out of American iron, German steel, or Japanese tin cans. Being unable to appreciate them all is missing out on a world of great things.
But thats just MY opinion! :P