Carlos Monzon smoked up to 100 ciggarettes, and fought often 15 rounders. His trainer Almicar Brusa said: "For all of the years that Id seen him, Monzon never gasped for air" Now that is stamina!
Marvin Hagler- he fought the 15th round like the 1st, and was always in tip-top shape, and he always got stronger as the fight went on..
Armstrong Sanchez Ali Calzaghe Marciano Those names came to mind 1st, there are likely many more on the same level tho.
Battling Nelson Harry Greb Henry Armstrong Salvador Sanchez Rocky Marciano Joe Frazier Many, many more.
For their size, Marciano and Frazier have incredible stamina, and I think it is superior to others in a p4p sense.
smoking i think increases your air capacity in the lungs but then again smoking kills (it just makes you look cool)....
This is what I would say or Chavez. Hagler and Chavez fought similarly in someways, although Hagler was a harder puncher and southpaw. So Marvin was even better than Chavez. Remember how easily Marvin dismantled Tony Sibson?