The belt pulley on the magneto has a mark on the outer edge. Align that mark with the center of the safety switch button. Assuming somebody hasn't removed the safety switch. In that case align the mark where the switch should be 1/2 way between the two switch mounting holes in the distributor bracket
While you are doing this, needless to say, the flywheel needs to be aligned with it's marks.
OOPS, you did say 1960 didn't you? That is different. The safety switch is in a different location, so the above instructions won't work.
You will find a mark on the belt pulley. You will also find a mark on the breaker plate. But wait--the breaker plate moves with the throttle. So you first have to position the breaker plate. If you look at the mark, you will see it extends down across the bottom of it. The lower end of the mark is then aligned with a mark on the bracket by adjusting the throttle. Now you are ready to align the pulley mark so all three are in alignment.