I used know of some site I found a long time ago, that had a black and white lobby card with a still shot of Godzilla to the left side and next to it said on the right side something like.
"Come see Godzilla Triple Feature at your local drive in
Godzilla on Monster Island
and
Godzilla vs. Megalon
also
Godzilla vs. the Cosmic Monster"
And I think it probably listed Cinema Shares and Toho on it. It seems like the year was close to either 1977 or 1978. Another Youtuber, uploaded a textless version of the tv spot and said it was 1978.
https://www.youtube.com/watch?v=yzULAaq2M-s
So, I thought that was probably the best bet since Godzilla vs. Megalon was shown in US theatres throughout 1976, and in 1977 they showed Godzilla vs. the Cosmic Monster and then Godzilla on Monster Island in the theatres later that year. That was I think about the only other time the films were shown out of order the first being Monster Zero after Sea Monster, Son and DAM.
Sadly I can't find that site or anything close it, I tried looking, but the closest I could find was this thread on Blu-Ray.org, where a user, "Wolfschimt" mentioned seeing it. https://forum.blu-ray.com/showthread.php?p=17053991
Also, I'm pretty sure that the lobby card list showing them in the Japanese release order, though the TV Spot has Megalon and Cosmic Monster swapped.