Jack fought 20+ rounds back in the day and he was just a defensive and graceful machine. Ud for Johnson
Liston would be difficult for anyone who is not a runner and Johnson was not a runner ... while I favor Johnson Sonny would be very dangerous ...
I tend to favor Liston in this one. Liston could punch but he was also a decent boxer as well. Sonny also had a very good jab, something that Johnson rarely had to deal with back in his era. With his 85" reach, Liston would reach Johnson with it and set up his right hand. A prime Liston would be the most dangerous fighter Johnson probably ever faced. Johnson wouldn't be able to manhandle Sonny like he did against much smaller men like Burns, Ketchel and Flynn. I take Sonny by late round KO. A decision by Johnson isn't out of the question but Jack would have to be at his very best against a prime Liston.