Here are the numbers from the Campagnolo website. We are talking about a lugged Italian frameset after all. I just copied and pasted the numbers from the chart. The measurement in mm is from the center of the BB to the center of the slot in the brazeon. The next number is the chainring size associated with that measurement and the string of seven numbers is the list of compatible chainrings.
Cissell, I only do lugged work and measure off the top of the BB shell once I have the ST pinned into the shell. If you are working with the Sachs tab, locate the reference hole and place it at 90° from the front at your preferred distance. Make a little stick with a mark for quick work. You can see I've used paint sticks. You can +- it a mm for customer needs. This advice is based on standardizing your parts. You can see what I use below. I just stuck a stub in a shell for illustration purposes, but you can get the idea. I use 119mm for my stick. You can also see I have another stick for placing bottles where I like.
Good luck, Craig