Since it's easily quantifiable with a heart-o-meter, I'll just see what it says on heartometer.gov/pugilist-studies-seventies-heavyweights/. ...Ah, yes, here it is. Frazier: 10.0, Chuvalo: 9.6, Quarry: 8.1 There's a 4.55567% margin of error and those are not definitively peak readings, only the readings taken on the day they were tested, except Quarry who was tested on seven separate occasions and the listed amount is his heart average.
In a way its insulting to sit in an armchair and try to quantify this quality in other obviously brave individuals, George Chuvalo has of course undergone so much heartache in his private familky life how could you fail to salute him and the other individuals.