Thanks, rvirgil. Thanks especially for the link to the wiring diagram on the MF 35 - showing NEGATIVE ground. Interesting, indeed.
(Everyone else ignore this paragraph so as not to confuse anyone). Brother has a MF35 manual on a CD for his tractor. He printed out wiring diagram. He and I looked at the diagram. His concern, then later mine, was that his diagram showed POSITIVE ground, while the tractor battery is installed NEGATIVE ground.
(I shall visit with him and learn the source of his CD manual.)
In any event, rvirgil, the link you provided reflects negative ground and his tractor is negative ground. Thus, will assume that electrical system worked fine as configured until the voltage regulator went bad - from whatever cause. Since generator has been rebuilt by "outside shop", is clean-grounded, wiring replaced to VR and new VR on the way - I feel much better about replacing the VR without fear of "destroying" it or the generator.