I’m stumped now. I just went through wheel industry technical references 1935 to 1949 and find no listing for a 13” rim. Nothing. No agricultural, motor scooter, industrial, construction, etc, applications at all. These industry references are what were used to standardize the manufacture of wheels before the government stepped in with OSHA and its predecessor agencies. K-H, Budd, Motor Wheel, Firestone, and Goodyear were members of the Tire and Rim Association and National Wheel and Rim Association so would have complied with their guidelines. So I’ve hit a wall on this.
Unless it goes back to my earlier comment about military applications not being referenced in civilian publications until many rears after their classification release. Who knows.
Like Gary suggests some modern 13” wheel or rim can be found that would allow the recreation of a suitable set of wheels. Stu