If he has the 10 lug wheels with 7.25" bolt pattern then 10R22.5 tires are out of the question.

Those wheels only came 5.25" wide, and a 8-22.5 tire is recommended. 9R22.5 will fit but are recommended for a 6" minimum wheel, so while it can work it's not exactly by the book either.

Couple years ago I got a $1,200 quote for 6 new tires installed.
in the meantime found a decent used set on Craigslist for next to nothing.

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-