Yes I have tried all of the caps. Yes I am putting them back in the right spot, not only are the numbered but I also took pictures of it when it came back from the machine shop.

To get the measurement down inside the block, I used all thread and some long nuts. All thread about an inch shorter than I needed. Backed the nuts off the all thread until it was tight (not crazy tight) going in and out of the block. Locked the nuts with secondary nuts. Took it out and measured it. I know it might be off a little, but certainly not .020 of an inch