Valley of Hunted Men (1942)

It's 1941 and three Nazis escape from a Canadian prison. Two are killed but the third kills Paul Schiller and assumes his identity. This leads him to the Three Mesquiteers ranch where his uncle Dr. Steiner is developing a chemical that will extract rubber from a local plant. The Nazis are out to stop the project and they get the fake Schiller to sabotage the Doctor's formula.