I guess once the paperwork has been turned into to the Department of Motor Vehicles, that's it, done. Rectification is done with semiconductor (selenium. I think) diodes. Interesting thing, there is a needle to indicate position, but there is no scale on the dial glass. I've attached a pdf schematic for the power supply unit, but the pdf for the head unit was too large - so here's a link:
https://www.rsp-italy.it/Electronics...-Schematic.pdf Hope it works.