Robert, I think you're mostly correct. These engines were supposed to be a hopped up Babe Bee with a large tank, and came standard with the Spitfire model, both early light green and later dark green versions. Not sure about the 90's reissue lt blue one.. These engines were available seperately, but packaged as a replacement part for the model, ie. no fancy box or card display.

Overall, decent engines, and would work well for a park flyer setup.

John