for a mild big block i woud not 0 deck it getting it squared is more what you want 00.5 to 0.10 the piston in the hole tru deckAnd go bore it this keep the bore strait to the deck and the deck squared to cam and crank center line .you can then put one piston and rod and check all corners BUT do you know all the rods are the same????are the pistons the same ??? are the crank pins the same index rods get recon and cranks get cut and i know cranks that have been off set to save them.and rods do get shorter and if it cast top piston they are not the same the new rods and piston that are cnc will help but you will have to check it and i would use a 0.39thick head gaskets