Emphasis on prime, I know nobody is gullible enough to believe that the shell of Leonard that lost to Camacho would have any bearing on what would happen if a prime Ray fought him. Camacho at 147 still had enough guile to go the distance with young Trinidad and De La Hoya. Does he see the final bell against Ray?
It is possible. Camacho at advanced age was nothing if not a good survivor, and against Ray he would know from the get go that 107-120 loss would be the best result he could ever get, doing his damnest to avoid contact. As he went full rounds with Oscar fairly easily (as in, wasn't close of being stopped), it is not given that Ray would get him out either
I also wouldn't be surprised in the least if Camacho went the distance. When up against it Camacho fought exclusively to not get knocked out. Run, hold whatever tactic required to achieve that end. Most opponents also won't bother doing everything in their power to get a knockout when they're already winning by a landslide. It will be a wasted effort when the opponent refuses to engage.
Also, the whipping Ray took in their fight might affect him psychologically, even if he were in his prime
Camacho was never stopped. Even in his last fight at age 48 fighting a guy half his age who hit him with everything, he was not stopped. A prime Camacho was a marvel to watch and would have given Leonard lots of problems. It would have been a great fight, no question, as I doubt Leonard could hit as hard as Rosario, the only guy that truly hurt him bad.
I think even the one that fought DLH would go the 15 round distance. If we get a prime Camacho, the one that had that tune-up against the Tom Hanks at welterweight, he may even win some rounds.