Stick with the 6 volt lamps unless you're willing to shell out at least 200 bux for the complete 12 volt points or
CDI (Capacitor Discharge Ignition) system.
You could always get a couple of those 110vac to 3-6-9-12vdc adapters, connect one to your 6v stator output (after running it through a bridge rectifier) to one adapters output set for 6vdc and then piggyback it the the other adapters input and set that adapter's output to 12vdc. Most of them are rated at 600ma, so you'd only get 7.2 watts, but hey it would work if you used an LED headlight........
I've seen weirder things......