Your regulator with B (Battery) F (Field) and L (Load or Lights) should also have an ARM or GEN terminal underneath. Battery is your battery connection, F to field on generator, ARM to ARM on generator and L supplies power to light switch. Ignition switch may power from L or Bat line
B F GEN same as above, Gen goes to ARM on generator. No Load terminal so switches would wire to a hot battery source
Unless there are reasons to keep it original, if it were mine I would consider an internal regulated alternator conversion. I'm reading a lot of reports of difficulty finding reliable generator regulators.