6-12v magneto conversion.

The magneto has no relevance to 6 V or 12 V charging systems.

You can buy a DVR2 regulator and have a 12 V charging system and lights.  Is that what you’re trying to do?

...purchase a V Reg from A O Services. This will give 12V or 6V. They come in Positive or Negative earth. You can change your voltage but NOT the polarity of the regulator.
It is recommended that you fit a 12V Field coil as well so that the 12V is available without the engine/dynamo having to be revved up too much. Perhaps your Dynamo repair man needs to involved with this job? A 12V Armature is not particularly recommended, they have been known to burn out. Battery and bulbs are of course very straightforward. BUT LED (rear and side lights) are polarity conscious, but they are available in Pos and Neg.