I've looked at the pictures and I'm absolutely sure one front wheel and one rear wheel are RH5° wheels, possibly others.
Agreed there are some other types of lock ring 20" wheels, hard to say how many with the info/pictures given.

Grigg

Last edited by Grigg; 12/03/2013 8:44 PM.
•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-