Factory overbore

Maltese cross indicates one or more bearing journals are .001 under. Cross with an X means all are under .010 or some, look on crank counterweight #3 for M1-10 or R3meaning main 1 or rod 3 is .010 under, etc. An A after the serial number on pad means a cylinder is .020, (didnt say pistons) a diamond means a lifter(s) are .008 OS and a O.S on the head means a valve guide is .002 over. This is from the 66 FSM.