Ingemar Johansson (1958) vs Michael Spinks (1985) 15 rounds. Remember what Ingo did to another boxer who later went 12 with Sonny Liston in Sept 1960, Eddie Machen, he starched him in one round on Sept 14 1958. It's the Ingo Bingo vs the Spinks Jinx, who wins and why?
If Ingo can land his bingo, he could win by KO. However, Spinks is too clever and he hit more than hard enough to hurt Ingo. And 1985 Holmes was still a more formidable opponent than any version of Ingo. I pick Spinks via mid to late round stoppage. Especially with Spinks weighing 200-205 pounds.
Spinks has the chin to survive Ignos right hand and use his reach and awkward style to outbox him. Close decision for Spinks.
I don’t think Spinks ever proved the chin to survive that right hand. That’s not to say he couldn’t, but it’s certainly no given imo
Ingo did not weigh over 200lbs but remember what he did to no.1 ranked Eddie Machen on Sept 14 1958, KO1, then bounced champion Floyd Patterson up and down the ring on June 26 1959 in Yankee Stadium before referee Ruby Goldstein rescued Floyd who appeared to be fighting to the 1959 tune Sleep Walk from Santo and Johnny after tasting the famed Ingo Bingo.
I think the surprise factor of Ingo being an unknown quantity to both Machen and Patterson played a large part in Ingo's success against each of them. Ingo's chances would be greatly increased if Spinks would be fighting Johannson in 1958-9 without having an advance opportunity to see him in action, as was the case with Machen and Patterson. If the fight takes place in the Spinks era, I think Michael would have to definitely be favored because of the advances in video technology which would afford him the opportunity to adequately prepare.