This is a tough fight to call. Nino was pretty slick, and, may be able to outmaneuver Gerald for a points win. But, with the G-Man, there is always the possibility of an early rounds KO if he catches Benvenuti clean.
How long after the weigh in is the fight? If it's the same day, GMan would either lose on the scales or be in no fit state to fight entering the ring. If it's c.34-hours before the fight, Nino would be giving away substantial amounts of weight.
Let’s just pretend Benvenuti is a natural 154lbs fighter in McClellan’s era, instead of being a natural 154lbs fighter in his actual era. So McClellan still has a size advantage, but Benvenuti is a natural 154lbder in McClellan’s era. And therefore in this scenario, the difference in size between Benvenuti and McClellan is the same size difference as between Benvenuti and Monzon.