Here's the rockin' theme song to the US version of Gammera The Invincible. It's by the Moons, and it's mostly instrumental. It's heard in the beginning of the movie as Gamera makes his way across the ice. It's quite possibly the best giant monster theme used in the movies, with The Green Slime a close second.
I'm not sure who the Moons actually were, or if they had much of a career. Doing just a bit of research shows me they at least had neat sound and some cool songs, at least they were hits in the UK. Wonder how they got chosen for this gig?