Hello ! Tracking down my block, it looks like it is out of a B-Body 68' Pontiac. I believe that was Bonneville, Catalina, etc.. since it is a YC block code 9790071.

Question, how would I know what the factory bore was and if it was bored out ever ? I can measure the bore i.d. with a set of digital calipers, but wouldn't know what to compare it to. Also, is there an easy way to tell just by looking at it ??
Thanks.