Our 8-18 volt Voltmeter is just the ticket for that 12V conversion you are performing whether using a 12V Generator or upgrading to a Delco or Denso Alternator. This Voltmeter comes standard in all of our 12V conversion wiring systems that have an Alternator doing the charging chores. 
NOTE: Ammeters and Alternators do not mix! Be safe! Can also be used with a 12V Generator as well.