For comparison sake 190 lbs Bert Whitehurst went the distance twice with Liston, Whitehurst was KO'd twice by Archie Moore, Rocky KO'd Archie Moore.
I just have to say I find it very funny when we all try to determine who would beat who from different time periods. God knows we have a hard time getting it right in the here and now. I personally think any fighter rated in the top 10 would beat 90% of the fighters that aren't in the top 10, Not many people have Liston in their top 10 but most would have Marciano in their top 10 even if it were closer to the bottom then the top. To say an undefeated fighter would have lost is hard for me to digest, Especially Rocky too tough, too strong the best conditioned boxer ever. The word lose wasn't in his Vocabulary. Rocky would wear him down and KO him like he did the 43 boxers before him.