I have Mandingo over Ringo in this one. Tough fight but the somewhat more skilled Norton finds a way to win.
The concern I have is Ken Norton's weakness to a fighter who could bang with both hands. If you are a boxer, then Norton fights his best fight, but if you can hit, then Ken folds like a stack of cards. Oscar Ringo Bonavena was extremely awkward, but he did have a punch, look what he did to Smoking Joe Frazier on Sept 20 1966, he decked Joe twice in one round, only to lose a hotly disputed 10 round decision. I know Frazier won the rematch in 15 rounds on Dec 10 1968 but the mere thought of Frazier on the canvas twice makes me wonder how Norton would be able to withstand Ringo's right hand.
Providing Ken does n't get caught during Oscar's charges,his better boxing - especially his jab- sees him through to a clear yet hard fought decision.
If it’s a distance fight it’s comfortably Norton’s imo. Obviously a better all round boxer with a great jab. That doesn’t preclude Oscar managing to shake and wobble Ken early. Norton’s chin was actually pretty good up to a certain point on the Richter Scale where he fell apart - Oscar might push him close to that threshold but not all the way into it. Best case scenario for Norton imo would be a later round KO/stoppage. Norton could hit very hard particularly when he got in to the offensive groove.