There's a guy who has an American Flyer layout he displays at several local train shows that has a few Lionel Scout type boxcars that he put Flyer trucks on and runs on his layout. They are a pretty good fit. I would imagine most of the starter set sized rolling stock would look OK running on Flyer track.
And some of the Flyer S gauge stuff was originally made for O gauge track before the war, so apparently it can work both ways.
J White
