I had a Dodge club cab pickup in the 70's, with jump seats facing each other behind the front seats. I used the truck for traveling around the country for a year and half and made a plywood platform to cover that back seat area with plenty storage underneath. No pics from back then, though.
I initially made the platform to hide all the stuff I stowed behind my front seats, but found quickly how nice it was to have an additional flat surface area. The platform went all the way from one side to the other, and was just below the top of the front seats by a couple inches. The ends of the platform rested on the top of the back cushions for the jump seats, which were under each side window.
I made it with a piano hinge in the middle so it folded in half and I could easily remove the whole thing for storage. It also made it possible to flip up one half or the other to gain access to that side's contents without removing the whole shelf or having to stop and open the door.
I made a simple upright out of the same plywood to hold up the center under the hinge. I can't recall if I made a ledger strip along the backside of the cab, but think the end supports and the center upright was enough. The plywood was thick enough to span the distance without bending, even with no support along the front edge.
As we traveled and the shelf's purpose evolved, I made a cutout in the half behind the passenger seat to fit a cheap styrofoam cooler for day use and trip snacks. We had a larger fridge in back. Sometimes we just used that front cooler as an easy access storage space. When we had food/drinks/ice in the cooler, it stayed cooler longer because most of it was below the shelf surface in the dark. Only the upper couple inches were above. I eventually made a cheap insulating sleeve for the lower portion.
On the driver's side I made another simple cutout approx 12x24 or so. I used the cutout piece as a removable lid with a finger hole, no hinges. It rested on a simple ledge all the way around attached to the bottom side of the platform, so the lid stayed flush. I kept a blanket on that side for my dog, who loved laying there on trips and was able to better interact with us and stick her nose out the window over my shoulder as I drove.
The same sort of affair could be done for full-sized seats and would allow for even more organized/contained/strapped down storage.
Just brainstorming, but I'd set up one platform to rest on the seats with a soft wedge where needed to make it level, enough support on each end so it doesn't compress the cushions all the time, and some sort of canvas or other fabric to protect the seats from abrasion when underway, if the platform in fact rest on the seats. Then another platform just below the top of the front seats, supported where needed and with cutouts if desired for occasional access from the top.
If concerned about the span and the amount of gear potentially on top of the upper platform, I'd attach a stiffener to the underside of the platform itself, not make a frame all the way around to hold it up. Simple works better sometimes. You could install a couple
footman's loops to the vehicle around the perimeter of the platform as attachment points, if necessary, or a simple aluminum bracket or angle underneath where needed.
The space between the platforms could have simple drawers, boxes like the FRO Cub Packs or Flat Packs (link to a
recent post about those), pull-outs accessible from the side doors, or whatever seems most effective and efficient, depending on what gear you want to stow there. A couple long spaces, couple short boxes, etc.
Having that upper platform made it easier to store more stuff in my case, and easier to then use the upper platform as an additional flat surface when needed for maps, etc, both while underway and when stopped.
What a cool opportunity to come up with an innovative solution for a huge space.
Now I'm intrigued to see what you come up with.
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