G'day worldrailboy,
A number of minor lines in Japan used rail trucks like this. The Nemuro-Takushoku Railway in Hokkaido had a number, some of them streamlined.
http://www.kk-net.com/~tabuchi/dragon.htmSimilar types of cars ran on the Kujukuri Railway, and one of the narrow-gauge Kintetsu predecessors had them as well.
I don't know the origins of the nickname "Galloping Goose" for the Rio Grande Southern railcars, but the boxy rear bodies were purpose built for them, they weren't old boxcar bodies.
Cheers,
Mark.