Pic three looks like a drivers seat mounted in the passenger side over the tool box. No wait, is there a tool box under the drivers seat? I didn't know there was one located there. Now I'm curious. Do you have an overall pic of the inside?
It is a very clean Marine M170!
Looks like the drivers seat is installed on the passenger side and a M38A1 drivers seat is installed on the drivers side. Maybe it's a radio jeep version which might explain the lack of holes in the tailgate and the odd seating. I didn't see any stretcher rails on the floor or the elusive upper stretcher rack. It also has the M38A1 passenger dash grab handle versus the upper stretcher bracket. I am curious now as to what the dash tag says by the grab handle to see if it says something about it being a radio jeep. It is definately a worthy project.
At this link it shows a Marine radio M170 and it is missing the spare tire carrier and it has the holes. M170_Willys_Jeep_Ser_10236_Georgia_USMC
Looks like you have some research to do. If you are interested you can see my M170 project on willysmjeeps under the gallery page 5 rdsar2k. You will have to register to see it.