Let's see...
Bud Wilkinson, born Apr. 23, 1916 -- coached St. Louis football Cardinals, 1978-79, went 3-10 in 1979 season...only 63...oh well, I think he was oldest head coach in the league at the time, but obviously not in history.
Marv Levy, born August 3, 1925 -- coached Buffalo Bills, 1986-97 (72).
George Halas, born Feb. 2, 1895, coached Chicago Bears, 1955-67. (72).
So apparently, Halas was the oldest head coach in history.
He was the only one I could think of.