User blog comment:ShodaiMeestonLarva/"Godzilla vs. Kamacuras" and "Godzilla vs. Bagan": Real or False?/@comment-831485-20150802101307

The extensive, but rarely published American magazine "Japanese Giants" had a detailed article on "GMK" in issue 9. And from Shusuke Kaneko himself in an interview, he notes that Kamacuras was his original Godzilla film plan, hoping CGI and modern day puppet effects could update the insect in spectacular ways. Those plans were quickly shelved however, when "Godzilla vs Megaguiras" was officially announced at Toho. Kaneko went onto "Godzilla vs M" next (the one with the mutant astronaut), and than the predecessor of "GMK" with Varan and Anguirus. And the rest, as you know, is history.

As for "Godzilla vs Bagan"...No clue.