Most 3-brush generators don't have enough current capacity to benefit from trying to use a 3-unit regulator. There's a reason GM didn't just decide to design a new regulator, instead of developing a complete new system. Moving the third brush in the direction of rotation increases the output, so if you decide to do it halfway and overload the old generator, max out the brush movement as far as it will go and set the current regulator to a fairly low reading, 20 amps or so. It makes no sense to do that when there are balanced systems available with the right generator included.
Jerry
