The info you're looking for is in this tech tip
http://www.stovebolt.com/techtips/wheels/

And in it is this link for the Accuride catalog.
http://www.accuridecorp.com/files/2012/10/Accuride-Wheels-Product-Catalog-Summer-2011.pdf
Page 48 gives recommended rim widths for different tire sizes.

225/70/19.5 work on 6 or 6.75" rims. As do 8x19.5 tires (and 5.25" as well).

I've not yet seen a 5.25" wide 19.5" wheel so I'd guess you have 6" wheels and could use either tire size you choose. Still worth checking your original rim width.

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-