You're apparently not using a stock switch so it's hard to tell how it was made inside but generally speaking 12v systems carry half the current that a 6v system does. Moving to 12v meant that the wiring, contacts etc., could be made lighter gauge (read less copper and brass, less money).
Taint that much money for the proper ignition switch, that's the way I would go.
Denny Graham
Sandwich, IL
