...square out the head n block by tramming in the oil pan rail. while you are on the bridgeport drilling you new holes.(thrugh a guide bushing in the cap) Dont forget to spot face the parting line before you try to tap it!!
Then when you bolt on #4 cap make a skim cut across the TOP of the cap this will then be parallel to the parting line giving you a good clamp ability in the vise to cut the thrust surface. Yes take a measurement from block thrust surface to cap...cut some off cap faces....replace and RE-MEASURE making sure your NEW cuts are square with block surfaces and parallel to block thrust surface.. ONCE you achieve face cuts that are parallel to the blocks thrust face....then you can indicate cap and finish it up. Yeah its alot of back n forth but takes longer to type it than to actually do it. Been a Journeyman Tool & Die & Mold maker for 30+ yrs. Also NO OIL while tapping cast iron