Kirby Grant was a violinist, a singer and a bandleader before becoming an actor, playing in a lot of B movies for Universal in the early 1940s, including Abbott & Costello comedies, and Westerns. Then he went to Monogram, where he starred with Chinook the Wonder Dog. This led him to the starring role of the TV series Sky King from 1952-59. After the series ended, he did very little acting, but made personal appearances, and traveled with the Carson & Barnes Circus from 1967 to 1970. Although Sky King played for many years in in re-runs, got received no residuals. He was killed in an automobile accident at the age of 73.
Howard Duff appeared in many film noir movies in the late 1940s, as wel as a few Westerns. He was cast on radio as Same Spade from 1946 to 1950. The show appeared on three different networks over it's run. But then, after his name was listed in the report Red Channels as a Communist subversive, he was fired. He later went into television, starring on Mr. Adams and Eve with his wife, Ida Lupino, and the series Dante. He also appeared in episodes of Bonanza (as Samuel Clemens, aka Mark Twain), The Twilight Zone, Combat, Burke's Law, Batman, and The Virginian. He played Det. Sam Stone on Felony Squad (and also on episodes of Judd For the Defense and Batman), and would continue guest starring on TV shows until 1990, as well as appearing in the films Kramer vs. Kramer and No Way Out. He was married, as I mentioned, to Ida Lupino in 1951, and her influence saved him from being blacklisted, though the marriage was a rocky one. They separated in 1966, and finally divorced in 1984. He died of a heart attack at the age of 76.