Here is a progress report on the rear floor. New support crossmembers have been welded in place and the rear of the chassis has been patched up. I am now intending to use Buffalo board for the rear floor. This is waterproof plywood with a patterned non slip coating on one side. This board will be screwed to the supports from underneath.
I have also fitted a spare wheel winch onto the crossmember. This is from a Ford Ranger, and it lifts the spare wheel up under the car for stowing.