Yeah the jet version was the only thing I found here on Simviation, do you know where I could find the prop version? By the way, I don't think NASA likes you throwing around their parts for the space station doing barrel rolls

Also, the one I downloaded was listed as a "Super Guppy" as well, and NASA did get it from the ESA:
The Super Guppy aircraft was acquired by NASA from the European Space Agency under an International Space Station barter agreement. Manufactured by Airbus Industries, ESA supplied the aircraft to offset the cost to NASA of carrying ESA experiment equipment to the station as part of two future Space Shuttle flights. The new Super Guppy is the latest version in a long line of Guppy cargo aircraft used by NASA. Guppy aircraft were used in several past space programs, including Gemini, Apollo, and Skylab, to transport spacecraft components. The first Guppy aircraft was developed in 1962, designed specifically for NASA operations by Aero Spacelines of California.