So I’m starting the rebuild of my 1972 slant. I believe that this motor has never been touched. Got it out of the car and disassembled today. I pulled the pistons out to clean the carbon off the top (really thick). Also discovered the top ring on three pistons broken. After cleaning I reinstalled them so I could measure how far in the hole they are. The number 4 piston is marked STD. Is it normal for only one piston to be marked? The pistons all measured very close to .172 in the hole, EXCEPT the number 4 piston (the one marked standard) it was about .190 in the hole. Does this seem “normal”?