How far down the cylinder did you take your first measurement? If you measured up high (top 1/4 - 3/8" of the cylinder), it could be that a previous "rebuilder" may have gotten over zealous when removing a cylinder ridge to remove pistons. I would remeasure your cylinder bore at least 1/2" below the deck top, then re-compare your measurements.

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)