These would be grueling fights, tough fights, close fights. Holyfield lacks the raw power to tap into spots like Foreman, Shavers and Cooney did, with Kenny only being prime for one of those bouts. Norton matches Holyfield for power and has a heckuva overhand right and his left hook wasn't half bad either. Talking of stamina Norton went 15 three times at heavyweight, including one vs the GOAT and one vs the highly regarded Holmes while past his pomp in one of the great heavyweight battles. He's not shying away in the late rounds. There'd be very little between them in a trilogy IMO.
Norton did well against light hitters like Ali Young and the young Holmes. The prime Holmes who was a little heavier and stronger then when he fought Norton would have beaten Norton decisively. The Holyfield that turned back Tyson and stopped him would beat Norton up for a few rounds Kenny hangs on tries to fight back but eventually gets stopped.
I think Norton outboxes Holyfield. Though he had an awkward style he was better defensively than Evander. Ken knew how to make his awkward style work for him. Norton can match Holyfield physically, just as quick, at least as strong, great stamina. Norton was a little smarter and a little sharper. Holyfield would keep trying to get into Norton even if he is frustrated by Ken's counterpunching. I dont see a knockout but a solid decision for the Ken Norton.