A 12V conversion is a cop-out by people who are unwilling to go to the effort needed to make 6 volts work. There is a huge amount of information archived here on the subject, and I'll suggest you read as much of it as possible before making a decision one way or another. I'm dealing with a crippled right hand after surgery for an infection, or I'd be glad to waste a few billion more electrons than the ones I've already dedicated to the subject. Long story short- - - - -6 volt cranking/charging systems are perfectly adequate to get the job done, but they DO NOT respond to a piecemeal approach. Every connection and component MUST be exactly right.
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!