hey all ive searched the forums for previous entries with no luck but alot of great advice and tips. my question is by jacking up the rear and spinning the tire 20 x's and dividing by 10 does that require a factory tire or does the size of tire matter at all? i have a 71 cheyenne 20 3/4 ton 350/350turbo the diff is 10 bolt and i believe when i got it i was told 456 im un able to get # from it at the moment. if some one can confirm spinning the wheel i would appreciate it thank you all

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