[Yosemite Sam]

It really sounds like you have recently replaced the voltage regulator with an "incorrect" one.

Or you have the small wires in the wrong places on your S/G.

Or you have a bare wire somewhere, perhaps one is pinched between the engine and frame.

If it didn't do this before, and there were no changes made to any electrical components during the transplant, then it shouldn't be doing it now. If none of the above conditions exist, then I would suspect that something came loose during the transplant and didn't get put back together properly.

Try putting the V/R from the 105 in it and see what happens.