Converting to 12volt you will need a 12v coil. But even with the 12volt coil you will need a resistor wire or a ballast resistor between the ignition lead and the coil. The positive side of the coil cannot take a constant 12volts. The distributor side of the circuit is not voltage sensitive - it is merely making and breaking the path to ground - which allows the coil to energize when the circuit is closed and to induce a spark when the circuit is broken.