The four-speed manual-clutch motors with 6V points ignition use a different taper on the flywheel end of the crankshaft than other versions.
The three-speed auto motors with 6V points ignition have their own taper.
I believe all the tapers are the same once you're talking 12V breakerless ignition, but it's a different taper than either of the 6V points ignitions. The part you linked to is for a 12V electronic system, and will be set up for that taper. As will all the inner-rotor kits and current aftermarket stuff.
Somewhere on this site is a thread--a sticky, even, I'm pretty sure--about putting a 12V ignition on a 6V motor. I think it was an ATC70, and I think the author might have been the artist currently known as Z. The thread mentions adapters available on Ebay enabling you to use one kind of flywheel on another kind of crank. I have not used these myself.
http://planetminis.com/f14/cdi-conversion-possible-103631.html
Dr. ATV has a replacement stator/flywheel for four-speed 6V points motors in their performance section (and probably in the CT70H section, SL70 and XL70 section, etc.) but I'm not sure whether it's more Mitsubishi or Hitachi style.
One approach would be to say, as I am kind of doing myself here, "Hey, these Mitsubishi setups are seeming more scarce. Maybe I ought to pick up a used Hitachi stator and flywheel instead, at least as a spare, in case the Mitsubishi needs nonexistent parts at some point."