Cylinder diameter VS. piston diameter
I have a few questions about an engine I just picked up. The guy I got it from told me it was a 327, but the casting number points to a 350. So I measured the bore and the stroke and determined that it was in fact, a 350. Using a micrometer I found that the cylinders are within 4.020 to 4.030 inches and the stroke is almost exactly 3.48 inches. So my question is this: I know that a stock 350 has a bore of 4 inches right? So why am I measuring 4.020 - 4.030? Is this engine bored over? Or is the piston what's supposed to be 4 inches? If I were to replace the pistons, what "bore" would I purchase, and would that "bore" be referring to; the actual piston diameter, or the actual cylinder diameter?
To be more specific I suppose, what is the stock 350 ACTUAL measurement of the diameter of the cylinder as opposed to the piston, and what tolerance should I expect in between the two?