I think you would encounter some serious problems with trying to use the 12 volt field coils and armature with a 6V regulator. Where are you in Tennessee? I've got several 6V generators on hand, and I'd be happy to work out some sort of swap with you and help set the regulator correctly. I've been doing this auto electrical stuff for 50+ years, and teaching it in high schools and trade schools for over 30.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!