Willard was a special height for his time. I was going to do this question for Primo but Jose Santa was taller than him.
I'm not aware of Willard fighting anyone tallter than himself, but there were a fair few big lads around the same time as him. Fred Fulton was the same height, and was going to challenge for his title, but the fight never ended up happening. There were objections to it going ahead because of WWI. He fought Carl Morris and Luther MCarty who were 6′ 4″, two of the more notable white hopes. Carl Morris had a win over the above mentioned Fulton, so not a bad contender. Luther MCarty was the most promising of the white hopes, but died in a fight. If I remember correctly he went into the fight with an injured neck, I think from a horse kicking him, but that's just off the topic of my head. I don't really feel like going through every one of his fights to find out though.
Hard to say. Bull Young who Willard killed in the ring, was purportedly a very big heavyweight. When the weight classes were broad, the big men of the division, often ended up fighting each other.
John "Bull" Young was indeed a big heavyweight. Height wise, though, based on pictures I've seen of him standing next to other boxers, whose heights are known, I'd guess he was about 6 feet 2 inches, and no more than 6 feet 3 inches.
Good post I'm not sure about Willard. The obvious one for Vitali would have been Valuev who I think he would have beaten quite easily.
Btw, speaking of Valuev's wingspan it was 85 to Vitali's 79, but as far as arm lengeth Vitali's was 29.5 inches compared to Valuev's 27 inches. Wingspan can be a deceiving measurement.
A report from before their third fight aid Willard had a significant height and reach advantage, so that sounds about right.
In Willard's last fight he took on Luis Angel Firpo. Although smaller than Willard, (6'3"?) he was nevertheless a big man by any standard.