you need a dial indicator and a magnetic base to measure it. set it up on a cam lobe and gently pry the cam one way and set the indicator to zero then pry the other way. note the reading.
you drill into the main oil galleries then tread and plug the. the heads get full time oiling from the main gallery. the cam bearing doesn't share any oil.
you then turn the bearing so the holes don't line up to the head oiling passages.
get a moly paste, say from isky cams, and brush a lot of it on the lubes and lifter bottoms. that bottle of stuff from mopar goes in the oil not on the cam.