I'm in the process of doing this, but from what Irish Rich said, the Pollak marine switch will allow me to use the threaded "M" terminal as a ground for the magneto...that's pretty rad. Everything on with the same key switch that I had on it before. It was a simple matter of pulling the other ignition and now I just have to run one more wire.
Now to figure out whether or not to get rid of the battery and replace it with a capacitor.