I'm assuming you want piston to deck distance for (A) a SCR number and (B) possibly achieving quench (.040). As said I would FIRST mockup the short block & measure all of em (as said the deck bridge/micrometer works OK) or at least the corners which will tell you how much to mill the block & you can potentially swap rods around if that will get em all more even or alter the rod C to C lengths slightly when you have them rebuilt & that is much more critical IF you are desireing quench as opposed to just getting a reasonable SCR number, then dissassemble it all for final balancing. Alot of work but when the long block is right it is right & with the right cam/intake/carb/converter & ign tuning & some spot on tuning you will have the BEST combo that YOU are capable of producing.