This is easily in my top three favorite Frankenstein movies (his bloody terror notwithstanding). How could it not be with two giant creatures battling it out in Japan? It's as close to Frankenstein vs King Kong or Godzilla as we will ever get. This might be the first movie Frankie got to be the hero in!
I wonder why there hasn't been a better US trailer found. Every one I've ever seen looks all washed out. Still, it's very indicative of what's going to happen in the movie. Good ol' AIP, never a bad trailer.