Bore size: bore is honed for piston size usually within .001 of piston skirt size. Crown of piston is smaller than skirt you may find some dimensional drawings on a piston makers are like probe or wiseco.
I'm no machinist but....Not so sure about tossing that out like that. Piston manufacturers typically spec their size & clearance based on the skirt (widest part). Some have different location but 1/2" up is what I've done. 1 thou clearance & you're going to lock a race piston right in the bore as soon as it warms up.
