Marciano v Kovalev

Marciano was 5'10.5" tall with a 68" reach.
Kovalev is 6' tall with a 72.5" reach
The weight difference would be negligible.
Spot the difference between this and a Golovkin matchup?

 

We know Marciano was floored by a 39years old ex hvy,is it beyond the realms of possibility that Kovalev could duplicate that feat?

 

It means Marciano could be floored in this match does it not ?

 

I'm not sold on Kovalev , but he appears more mobile than Lastarza , and he has some power, he might hang around for a while.

 

With you perhaps.
177&180lbs Ted Lowry went the distance twice with Marciano ,some thought he won the first fight including the local press which were on Rocky's turf.
Accounts say that Lowry had Rocky in some difficulty and Lowry could not hit like Kovalev.

"It was Lowry, not Marciano, who was on the verge of scoring an early knockout, stinging Marciano with two terrific rights in the first round and then rocking him with two mighty uppercuts in the second. By the fourth, a staggered Marciano seemed just one punch away from being knocked out. But then, inexplicably, Lowry stopped fighting and retreated into a shell despite warnings from the referee to open up and a cascade of boos from the crowd. To many, it appeared that Lowry was deliberately carrying Marciano. Was foul play afoot? Was Lowry getting paid to lose? Or was he merely tiring? Whatever the reason, a revived Marciano managed to rally in the late rounds even though many of his punches missed their mark or lacked force. On the basis of his aggressiveness and constant punching, Marciano won a unanimous decision from the judges. Most observers felt, however, that Lowry should have won."
Lowry, who earned $2,500 for the fight, denied he threw the fight. "I beat Rocky that night and that’s it," he said. "He changed his strategy in the fifth round and made a fight of it, but I won two of the last six rounds after winning the first four. It was a hometown decision."

I don't think your point is valid at all.