"Filmed in 1971, the film follows David Aldana and the Summer Grand National races, but the cameras just happened to get Bart Markel’s 28th and last national win at Columbus, Ohio. This seldom seen movie shot over 50 years ago includes great footage of Dick Mann, Gene Romero, Jim Rice, Don Castro, Eddie Mulder, Mark Brelsford, Cal Rayborn, Chuck Palmgren, Keith Mashburn, and many more great riders of the day. American Flat Track at it's best!"
https://thevintagent.com/2021/12/01/the-vintagent-classics-the-thrill-is-on/