He did about 1/2 of the movie when he had a massive heart attack & died. His part was reshot with Yul Brynner. Some long shots with his back to the camera is still him
Now, you see, when I hear the phrase "Old Chicago", I think of Old Chicago - the combination shopping mall/indoor amusement park that opened in sububan Bollingbrook, Illinois in the mid-1970's and went bankrupt about ten years later.
By the way, the site where O'Leary's barn stood is now the site of the Chicago Fire Department's training center.