Toney was a very good fighter in his younger & lighter days, but he was never in the class of a Marvin Hagler
Hagler would win this fight hands down. He would just be too busy for Toney. Toney would not be able to intimidate Hagler either. Hagler by decision.
The problem with this match-up is that "Prime" Toney, being a super middleweight, would come into the ring at 180ish, so it's essentially a middleweight Hagler fighting a cruiserweight. Give Hagler the same weigh-in rules, how much would he put on?