I would definitely favor Norton. But, a knockout win for Fitzsimmons wouldn't exactly be out of the question. I think a great many people in January, 1990 would have found it more likely than Douglas knocking Tyson out.
Norton, jab to the body, big overhand right and it wouldn’t take long with all of Fitzsimmons weight on his back leg, leaves him nowhere to go after Norton’s jab to the body, combined with the fact that he had his chin in the air, leaves him completely open to the overhand right from Norton.
Norton was not weak chinned, he fought monsters and got knocked out. Trying to frame a modern well regarded heavyweight as being able to conceivably lose to John L Sullivan and Bob Fitzsimmons using the fact he was KOed by George Foreman, Gerry Cooney and Earnie Shavers doesn't work as an argumentative piece for me. Sullivan and Fitz had cruder technique, worse training and altogether less artillery. Bob Fitz could not punch like Foreman, Cooney, or Shavers.