What a lovely thing to find, please enjoy while it is online (no copyright infringement intended, I did not upload the video, I found it, it is public on YouTube):
Gigantis – The Fire Monster
Now, as you can see, Gigantis is none other than the mighty Godzilla and in Japan this is officially the second Godzilla movie. For some reason the American distributor of the movie decided to rename the creature Gigantis, even though Godzilla had been a huge success in the USA, too. Suffice to say, Gigantis was not a sucess at all and no other Godzilla movies have since renamed the titular character, although other abbominations have happened (especially recently)
"Godzilla '54 design" by Source (WP:NFCC#4). Licensed under Fair use via Wikipedia.