Chad if you get a chance to see if you've got any books for the #7, that would be great!
I did pick up a parts catalog for Autopatrol #9 (9A1-9A651 / 8A1-8A577) power train & chassis.
Here is what it shows for rear tire assemblies. It looks like these two tires are mounted on a single wheel assembly?
Chuckb thanks for the lead. There are actually 3 dealers for Unverferth within 30 miles of me.
Thank You, Roby Whitehead

I have 3 auto patrol graders #7 #( and an early diesel auto patrol all are single rear akle with dual 9x24 tires i have seen the single tire setup and also the tandem drive but i believe that these were on later models I dont know if unverferth can make a rim with the lock ring but could make one with a deep center chuck