Martin Sheen (Pike) & Sam Waterston (White Bull) also worked together on Grace and Frankie (2015) as Robert Hanson & Sol Bergstein respectively.
Originally billed as the first British western to be shot in the U.S.
Interestingly, Martin Sheen had replaced Harvey Keitel on Apocalypse Now (1979).
The grey horse he steals, is actually an Arabian, not a mustang.