What we did was rotate the advance limiting slot inside the distributor from 18L to the 13L position which is 180 degrees off from where is was for correct timing. Since the dist. rotor slot (notch) in the top of the shaft is all part of that piece, you have to pull the distributor and rotate the gear that meshes with the cam 180 degress to get it back where it belongs. Look at the pictures that shows the advance slots. When you pull that up and rotate it you are changing the position of the rotor to.
If on the other hand you choose to remove the dist. and change the advance stops out of the car, when you put it back in with the rotor in the correct position, you would have actually changed the gears messing with the cam 180 degrees, but you may not have realized it.
If on the other hand, for advance slots that did not have to be rotated, but just springs adding, you would "not" do this.
Tell me if this is not clear enough and I will take a picture of my old dist. shaft I gave Jeremy with advance mechanism in the two positions so you can see clearly. Perhaps putting the rotor on will make it clearer.
The purpose of doing this was to help people that that were not familiar with the process. So ask any and all questions that will help so you understand.
Wayne