Take your present alternator to any Starter/Generator Electrical shop and get them to replace the regulator with a 12v unit. The ignition coil and the light bulbs are the two items that will need to be changed. I prefer the
Tickin-in Thru Time turn signal kit.
I know you didn't ask for my opinion, but I think you changing to 12v is foolish when it already has an operable electrical system.