[rotorwrench]

The high tension terminal of an adapter plate will still be functional with 12-volt if it was made for 6-volt. The only part of an ignition system that voltage matters with is just the coil. A 1.5 Ohm primary coil is usable on 6-volts. It requires a ballast resistor if used on 12-volts. Most modern can type coils for 12-volt systems have a 3-Ohm primary to use with no ballast.