I think many could have been used in the military and for Park service duty. The original Transport Yellow color of mine supposedly was common for Willys used by the air force.
Unfortunately, I think it would be pretty hard to track down the history of a specific vehicle unless you get lucky and find one with a good oral history to go along with it. The paperwork trail in most states goes pretty cold much before the 60's. I wish I could figure out more about the history of my wagon, but I only made it back to the 80's before I hit a wall.