Great video, 2nd half about the O2 (337)
Especially interesting is that during the Vietnam War, if you were a corporate owner of a Skymaster your aircraft was confiscated by the US Govt, and converted into an O2 for military use.
I don't know of any other General Aviation aircraft in history that was deemed so desireable by the US Gov. for its capabilities and performance, that they were conscripted
http://www.eaavideo.org/video.aspx?v=275367198001