zero deck pistons?

Best method of zero decking a block is to use the tallest 4 piston and rod assembly,one on each corner and then measure down to the piston from the deck at TDC,marking on the deck the measurement and do each corner.Once you have found the amount,you can tell the machine shop what needs to come off from each end.This is with the assumption that your piston/rod assembly not been blue printed.You need a depth mic and need to measure to the higest point of the pistons rocking the pistons to see if there is any change in the readings,on all 4 corners,MMT