Charging issues on a ‘64 Valiant...

Sounds as if it is not charging.

Please more details about "how' you converted the regulator. After the conversion, your alternator MUST have two insulated (isolated) field terminals. There should be "ignition run" switched 12V to one terminal, and the green wire going back to the VR connected to the remaining alternator field

If you simply connected the new VR in place of your old one it will not charge. In other words you need a '70 or later alternator with 2 field connectors.

From MyMopar: Here is what your old circuit looked like

MyMopar - Mopar Forums & Information - Mopar Charging System Overview and Conversion

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Abovethe VR is connected to switched 12V and feeds and controls power to the field and through the field to ground, controlling the charge rate

Below is the conversion

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The electronic regulator for 70 and later does NOT have a field (brush) to ground. Instead, one field terminal gets 12V power, and the green wire to the VR controls the GROUND side of the field