As much as I appreciate Harold's skills, especially at light heavy, and as much as I have reservations about Johansson's standing in the all-time ranking of lineal heavyweight champions, I have to go with Ingo. He had a devastating right by any standard, while Johnson's chin was suspect by any standard. Harold was the smaller man and he would have to press Ingo in order to land his punches and this would put him right in the middle of Ingo's wheelhouse range. Ingo by kayo.
Ingo was a flash in the pan who knocked out 2 superior top heavyweights who he surprised with his power. If Harold was as unaware as Machen and Patterson he probably gets KOd. If it’s after Patterson has come back and KOd him Johnson knows what to look for he probably wins a close decision but Ingos size and power could possibly allow him to take it.
Almost every time Johnson was stopped or hurt it was off of a right hand. At some point Ingo would land a right hand and that would end Johnsons night. Itd be ugly too.