Autosparks wiring diagram?

[JonE]

I'd start from the Cornforth diagram in a large clear room and lay it all out and work out what all the bits are. The regulator isn't original, but then you may not be 6V anymore - you need to scrutinise everything and work out what differs. You probably need a Ruby 6V cutout to get back to original - something like a CFR2 is featured in the Cornforth dia and arent too expensive to find secondhand. In fact, appeal on here...
But you may want to keep some of the charging system if its been "upgraded" (sic) if you can get your read round why and how!