Great news, everyone! Neo1024 has made the raw video of Tenguri, Boy of the Plains available for download. I've added the link to the Download These Fansubs section. He's now asking for help in providing a fansub translation for English subtitles.
Tenguri was made in 1977, and was Yasuo Otsuka's sole directorial film. Hayao Miyazaki helped out his friend with key animation in various parts. The style of this anime is very similar to Heidi, like many anime series of the 1970s, although this one-shot deal was somewhat obscure and easily forgotten. This movie was produced by the dairy industry, and that influence proved to be deeply frustrating for Otsuka. This likely explains why he never worked as director again. Animation was his realm, and would later work with Miyazaki on Future Boy Conan in 1978, Castle of Cagliostro and the second Lupin III series in 1979, and Sherlock Hound in 1981 (he helped out on one great action scene), and he worked with Isao Takahata as animation director on Jarinko Chie.
So Tenguri is an important piece of history for the Ghibli Freaks. We should work on providing fansubs for this short film.