It depends on the year of production, and which design of regulator is being used. Almost all late-design regulators are self-exciting, and really don't need the extra connection. I've been retrofitting farm tractors with the Delco SI for several years, and I always get the latest-model regulator and a new set of brushes from my rebuilder friend whenever I install one. They last about 3 days past forever on a farm tractor application.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!