I am rebuilding a 1963 Bonneville which had been converted by others to 12 volts. I don't know if it ever actually ran at 12 volts. The stator has only two green wires coming out of it. Every stator and every wiring diagram I've ever seen shows three wires. Does anyone know anything about this?

Assuming it is a true 2 wire and not a 3 wire with a lead broken off.... The 2 wire single phase stator is 12v(10 amp) 120w @ speed(not idle). It uses a 4 diode bridge and Zener to burn off excess power above 14.3v. The bridge rectifier is the normal lucas silicon rectifier or a modern encapsulated rectifier.