Zale missed a great portion of his prime to war service so perhaps you need to extrapolate a bit here. But both were noted for a certain attribute. I think you know where I'm going here.
Zale was one tough cookie but I like the bodysnatcher big here. McCallum is very underrated I believe while the "Man of Steel" is a little overrated. McCallum KO 11 Zale
Zales was typical of guys from his era..they were tougher and harder than anyone McCallum ever fought in general...although I liked Mike, he would he would be manhandled by an even better body snatcher than himself..a late round tko for Zale.
McCallum either by widish decision or late TKO, better boxer, better defense, excellent jab and he'd be faster for once too.
I think McCallum would outbox Zale and win a decision by a fair margin. Be interesting who has the better on the inside these two are some of the best body punches the sport has seen.
Never count Zale out. But I think Mike is to well rounded a fighter for him and can take a decision......
McCallum by decision but he would have to use his boxing skills if he gets into a war with zale he may find himself in trouble late in the fight