The original tach drive was on the back of the generator. There are no alternators out there that have such a drive and no kits that I know of to drive the original tach. Could use any 12 volt auto zone thach that signals from the distributor if you are not worried abut appearances. One other thought is maybe finding an original generator and having it converted to 12 volt if that's possible. I don't really have a good easy solution for you, this is all I can think of.