Yes, it means the 6v regulator will become a 12v regulator, the 6v gen will work fine on 12v. If the gen is worked on or removed from the vehicle, it should be polarized as the manual describes.
There is no need to change any parts in the charging system.
The ignition system and all other electrical devices will need to be updated. Depending on the ignition system installed, several changes may be necessary, including a ballast resistor, the coil, condenser, starter relay(solenoid). The starter will be fine on 12v but if there is a relay it will need to be compatible with 12v and the ballast resistor wiring. A relay may need to be added to address the ballast resistor issue. If the engine starts fine and is not started in the cold, the relay might not be needed. The condenser and ballast resistor need to be matched to the coil.
