During the 70s I saw what must have been a Japanese Godzilla movie. In fact it had three different Godzillas: a rocky one, a robot one, and a normal Godzilla.
Does anyone know the name of this movie?
I believe the movie you are thinking of is Godzilla vs Space Godzilla . The "rocky" Godzilla would be Space Godzilla, and the robotic "Godzilla" you recall is actually M.O.G.U.E.R.A, a mecha rebuilt from remains of Mechagodzilla.