Actually, it's THE TERROR OF GODZLLA, which I saw a fine 35mm theatrical print of in the 90s. It was the edited version though, which is sad. No real reason to edit it. This movie has had more titles and versions than most Godzilla movies, since it also had a TV version with the added prologue. It needed it, since after the opening scenes, Godzilla doesn't appear again for about 30 minutes or so. That's not a good idea for the 70s Godzilla.
This was one of the last Godzilla movies I saw, though I remember the first time I watched it vividly. It was late spring 1979 and I had heard this was a more serious Godzilla movie. I really enjoyed it then, though now it's fallen a couple notches. It's a fine send off to the original series, but it's not quite as good as the first Mechagodzilla movie. It's not as fun as the rest of the 70s movies. I can see why the series ended (as well as the other economic reasons).