If Monzon moves up in 1974-75, he is 32-33 years old. He might could try Bob Foster who is 36+years old and has the Ahumada draw waiting to occur. Galindez then moves in running interference for Monzon. But the "Golden Age of Lightheavies" is coming on line at the same time with about 15 really good LtHeavies around thereafter.
Can't see monzon doing to well against most of the light heavy s of his own era or there about s Longhorn tbh,but a few from other decade's maybe he has a shot. As the above mentioned Lalonde ,I'd say Carlos for sure .Carlos was perfect for middle but I think its possible he' could step up a little and beat a light heavy ,just not a great like spinks or even a old Foster.
Interesting match up.I reckon a tough fight for Carlos but winnable. Maybe by decision for Monza. Wonder how he'd do against McCallum at light heavy? Both middle stepping up.
It's impossible to know really, because he didn't even test the waters against journeyman type light heavies to gauge where he stood in terms of effectiveness, never mind good contenders or genuine elites. A fair chunk of his great success at middle came from him being so physically huge and monstrous in comparison to his opponents and knowing how to maximize his strengths and fight tall. Obviously he was very skilled as well, but I don't think his style would've carried up well against at least equally sized top fighters or naturally bigger ones. And he was a smart bloke who I think knew this and didn't risk hedging his bets.
Just like Hagler, Monzon knew he belonged at middle weight. Staying put and retiring when he did preserved his image. Monzon fought in the day when lower weight fighters were not shy about moving up, possibly because there were fewer belts back then. When I look over Monzon's resume, he won most of his biggest matches with a size and age advantage. He never really beat a natural middleweight in his prime with ability. Monzon who had excellent conditioning, a very solid chin, and a long jab / high punch output wasn't going to lose to smaller / older guys. Benvenuti was a natural middleweight, but his best stuff was in the 1960's, and he was past it by the time he met Monzon, as he was stopped by a 9-5-1 fighter a few months before meeting Monzon in1970. Griffith was 35 years old and stood 5'7 1/2" tall. Napoles was a former light weight, also 5'7 1/2 " tall. Valdes a former welterweight, had a reach of 69".
Monzon like Hagler later on, knew that he was ideally suited to the middleweight division...so showing a wisdom in his boxing life that he failed to show in his private life, he chose to remain in that perfect division....and I cannot knock him at all for that.