Exciter Wire with Early Regulator Setup
What do you mean "3 wire?" I would call the 69/ earlier setup a "2 wire" If you actually have a later alternator with 2 field terminals (isolated field, 70/ later) I would use the 70 / later regulator.
If the white is switched with igntion switch I would wire it to the regulator IGN terminal
Does this "Rebel" have a link to online destructions?
Simplified diagram of 70/ later
Pre-70--original alternator grounded field cannot be insulated