I was working as a Ford race crew member at the Detroit grand prix in the early 1980's. I met Carroll Shelby in the paddock, and we walked together up the stairs (a very long, long, flight of stairs) up to the car show. He was having a tough time getting up the stairs. However, he kept quiet about it, and simply pressed on, slowly.
My guess is that was prior to his heart transplant.
In any case, he was a very nice guy and clearly had a passion for Fords.