three brush regulator

[Brian]

When early fords were equipped with radios or other high electrical draw items, there was available, instead of the regular round cutout, a sorta oval regulator that attached atop the 3 brush generator. i think it contained a cutout and some sort of voltage control.
Over the years, from time to time, I have run 3 brush generators on 12 volt neg earth, using either fun products regulators or simply a diode fitted within the cutout housing. What would be involved in converting the optional oval regulator to handle 12 volts? I have finally sourced one and want to get it converted to be able to cope with the higher voltage.