Best methods are counting the teeth or jack up a wheel and count turns, each followed by some math.
Checking it out in person is probably less effort and time and more reliable than searching and speculating on the net.

Good luck!

•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-