[papajam]

With changing out the regulator, the generator may need to be 'polarized'. To do this, and assuming there's battery voltage at the regulator B+ terminal, fashion a jumper wire and momentarily jump terminals B+ and DF at the regulator. And yes, there will be a spark! Now start the car and using your multimeter, check for voltage at the DF terminal on the regulator. If it's not battery voltage, there's something up with the regulator. If there is battery voltage at the DF terminal, check the voltage at the generator DF terminal. It MUST be the same as the regulator DF terminal voltage. If it isn't, repair/replace the DF wire. If the voltages check OK, then the gennie probably needs a re-brush and a commutator dressing (or an alternator conversion).