Re: all tached out
If it has a 12 pole stator, just get 12 pole/6 pulse tach and hook up the signal wire to one of the yellow wires (from the stator) at the rectifier. It won't matter what type of ignition you have. I have run these type of tachs on Merc motors with Magnetos and Thunderbolt ignitions. Some tachs will have an adjustment screw on the back to set the pulse setting.
Do you already have a tach? Some tachs from Mercury or Airguide were more engine specific, as they got their signal from the switchbox or had a separate module (Airguide).