There isn't one answer to your question. My 1947 wheel listing says the 46 could have been set up with either 20x5s, 20x6s, 20x6.5s or 20x7s. Since it's a 1.5 ton you're naturally expecting the narrower of the options but, as you're seeing on your 36, wheels get changed over time. Even on your 36 the book shows your truck could have been sourced with 20x3.75s or 20x4.33s. The 20x4.33" was in later books called a 6" rim, but looking at the ones I have that are that size they look like what we'd today call a 5" rim. The standards on rim measurements have changed over the years and get confusing. Stu