Monzon would be the favourite but I could see toney beating him too. I meean James toney's prime was from 1991-1994, a much tougher era for the 160/168 division. Monzon and Hagler dominated during years where there were only a few good fighters in thier division.
people seem to forget that Toney's punch resistance wasn't near as good at 160 as it was higher in weight. he really drained himself making that limit.
This is why the day of the weigh in is key ... other than possible stamina issues, Toney would be a terrible match up for Monzon. Carlos' strengths were his strength, his consistent power, his size ... none of these were beyond Toney's proven ability against much bigger fighters from 168 and up ..however, Carlos could go a strong 15 and the weight issue is a deciding actor for James ..