1910 Jack Johnson vs 1905 Marvin Hart Scenario I: 1905, San Francisco, Alec Greggains referee, 20 rounds Scenario II: 1910, Reno, Tex Rickard referee, 45 rounds How do you see the fights panning out?
I think the referee is more important than the year. If Rickard had refereed their fight Johnson may have taken a decision. Neither man ever went 45rds, I wonder why you pick this distance? Is it because of the Johnson v Jeffries fight?
Yes, in the second scenario, I'm wondering how Hart may have done in place of Jeffries. (In the first scenario, I'm wondering how 1910 Johnson does in place of 1905 Johnson -- I get the impression that around 1907 Johnson began to get a bit more active offensively while still maintaining strong defense). Neither man ever actually went 45 rounds, but Johnson did schedule for it vs. Jeffries; also, Hart's bout vs. Root for title recognition was a finish fight. So I don't think there's compelling reason to suspect either man would have objected to the 45 round distance in a meeting. Of course, Hart would only have met Johnson in hopes of exceptionally advancing his own title aspirations.
I think that Johnson would have beaten the living snot out of Hart in any sort of rematch. He would have learned from his mistakes, and he would be looking to bring his own referee. Hart doesn't cast the magic spell twice.
Hart was a very durable man when he was in his short prime. I think Johnson would have beaten him, but Marvin might have been there for the finish.