In the Gentleman Prizefighter documentary, there is footage of this movie from the 40s featuring Corbett and Fitzsimmons. What is it called? This content is protected
You mean featuring their characters? Both boxers were no longer alive by the 40s. It could be a short film rather than a full-length movie. Shorts were often shown in theaters back then that recreated historical subjects.
Looks like it's Vigilantes of Boomtown - a western about a plot to get the fight cancelled by having Jim Corbett kidnapped. https://www.imdb.com/title/tt0039959/