I'm sure others have done this, but tonight I tried my automotive timing light on my S/S ignition and it worked perfectly. My light has a knob for checking the advance on distributors.
By setting the light to 5 degrees advanced the timing mark will move 5 degrees from the pointer. Then I can set the timing on Tiny 5 degrees advanced by moving the magnet relative to the crank until the timing mark lines back up with the pointer.
-Bob