"Maybe this is the place to get some answers from the Bill Warrens and the Tom Weavers, (Steve Ryfle? Is he on this board?) et al:

Was there ever an "alternate ending" in which Godzilla won?"

This link might help:
www.snopes.com/movies/films/godzilla.htm

I dont know where Forry picked up the idea that there was two endings. Probably another bit of the good ol' Forry ballyhoo.