During the Indianapolis 500 Joe races in, it is shown that most cars are using a "riding mechanic," as Joe does. The last year that occurred was the 1937 race.
Mexican-born Margo was given top billing as the most recognizable name in the cast, having appeared previously in the prestige screen production of Maxwell Anderson's stage hit Winterset (1936), the Shangri-La fantasy drama Lost Horizon (1937), and The Leopard Man (1943), one of Val Lewton's evocative horror pictures for the studio. This was her last picture for five years after marrying actor Eddie Albert (later of TV's Green Acres (1965)). The marriage produced the actor Edward Albert. When she returned to the screen in the late 1940's, she worked sporadically over the following 15 years or so, mostly in television, before living out the last 20 years of her life in retirement.
Robert Ryan was not yet the name he would become in his long run as one of Hollywood's most respected actors, despite being cast mostly in heavy roles. His star was beginning to rise at RKO with six pictures released by the studio in 1943, including the war-themed Bombardier (1943) and Behind the Rising Sun (1943), which also starred Margo. Just a couple of months after this film was released, Ryan enlisted in the Marines for the duration of World War II. When he returned to Hollywood in 1947, he became a key figure in the film noir genre that took hold after the war, with starring roles in such films as The Woman on the Beach (1947), Crossfire (1947), Born to Be Bad (1950), and On Dangerous Ground (1951). Ryan continued to create memorable roles right up to his death, making his final appearance in a film adaptation of Eugene O'Neill's The Iceman Cometh (1973).
RKO saved money and materials in this wartime picture by utilizing the studio's machine shop and entrance gate for the factory set in this film.