I have a 48 A that had already been converted to 12 volt system. The bearing went out in the altanator and im needing a new one. I took the old one to Orileys and they looked up the number on the altanator and said that it came off a 73 Ford F-100 6 cyl. They got one for 31 dollars.Its a Autolite that takes the use of a voltage regulator.The parts man said that it self polorizes its self.The guy said if I didnt want that one I could get a GM one wire. My question is do I just replace it with the Autolite or would it be better to get the GM altanator? I been told that some altanators you have to rev the engine up to 900 rpms to get it to charge. Which way would be better?