I am still struggling with my '63 and it's 6 volt lights. I have done several things to make them a bit brighter but still not to my liking. I have cleaned connections, added a ground wire, replaced ground cables...that sort of thing.
I saw a method of bending a tab in the regulator to increase the output a little but am very cautious about anything electrical...that's not something I'm good at.
Across the battery I get a little over 6 volts without the engine running. With the engine running and reving up slightly, I get about 6.4 volts. I'd like to adjust the regulator and see about 7 volts...seems like that would help the lights and the battery.
Has anyone ever tried this method of bending the stop in the regulator ?

So how do you keep the 8 volt battery charged ?

Yeah, me too. I've seen an 8 volt battery many, many years ago. If I could get another volt out of my regulator it sure would help. I tested the generator and it turned out sufficient voltage, so I think the regulator is the problem. I tried another regulator with the same result. I may bend the contact in one of them and give it a try. I'm just too lazy to do it right now.