Lights dimming and brightening

There is still another option.
Like I said before there is a solid state regulater that lookks identiacal to your original ( black box ) . With it you could hang a 60 amp square back altenater on the engine and simply ground its second field terminal on it just like the factory did on the your 36 amp round back alt.
End result is more amps and more stable charging system with no complicated alterations required.