Thanks for the added pics and video. The rear shot definitely shows the wide box heritage. Lots of potential there.
Hope you don't mind this ol cabinetmaker putting out some ideas for you to mull over.
For the bed, find some of the original metal strips from a wood floor bed. Get some clear oak or calico hickory milled to accept the metal strips. The wood will need to be finished in some kind of clear marine grade spar varnish, or similar, to stand up to UV and weather degradation.
Then build a full length bed floor that sets just above the height of the rear wheels. But, make the wood deck into a couple gull wing lift doors, like the old Mercedes sports car from the 50s. Inset some stainless steel fingerpulls into the wood and use some of the air filled lift cylinders to support the open doors.
I'm not sure what you'd find for hinges, but they would need to be a hidden hinge, like the euro style cabinet hinge, so the fact that they are functional doors would be hidden. (just had a wild thought, maybe hood hinges could be retrofitted and the pull cable latch system used to eliminate the fingerpulls and air lift cylinders) Under these doors make some bins to fill in the lower areas of the frame. This would give a look of the original bed and hide the fact that there is hidden storage underneath.
Don