Hi Bob,
I'm sure the first question is why do you want to convert to 12V? Is it just to power a few components? If so, you can get a 6V to 12V converter.
IF you are set on 12V, you can get a one wire alternator that has the regulator built in, therefore eliminating your regulator. OR you can get a 12V generator and use a regulator... Lots of choices.
There's several great articles and help in the tech tips section (with pictures) on here.
Enjoy!