I have done this. Put the vacuum advance on and all the way up the dizzy as you can. Put the dizzy in the block and you can "feel" it engage the oil pump. Then loosen the screw and set the vacuum advance down to the block. It will go about a 1/2 inch down from the shoulder. Next time if you are not engaged it will set above the block and you will know it is not engaged with the pump. It can be a bit fussy to get it right. After a while you will wonder what all the fuss was. pfarbers' trick is as good as I have seen. Think of this as a skill, like reading a micrometer. You gotta have it and you gotta feel it.
