What tires fit what rims is determined in part by the rim width, what rim widths are you considering?

I'm unclear if 20" radial tires will fit the old tube type wheels, part of that answer is the bead seat angle, the new tires MUST match the angle of the old. Check the Accuride catalog link above for some more info on that.

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-