Here's some info in our Tech Tips
http://www.stovebolt.com/techtips/wheels/

When my 1 ton is back on the road it will have 19.5" single wheels on it, and 8R19.5 tires.

You have a number of options though, some 16" lock ring wheels may be simplest to find and get tires for.
If you find tubeless wheels double check that they fit over the brake drums.

Grigg

•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-