A couple additional references to the jeep were made in the January 1943 issue of Popular Mechanics. You can see the online version at Google Books
1) Page 33: “Jeep Flies Target Plane to Help Gunner’s Aim”
Apparently, a plane was mounted to a jeep and driven across an open field. I’ve never seen any other pictures of this.
2) Page 64: Perhaps this is the first running model jeep? It certainly was an early one!