Carnera would most likely decision Ruiz. Ruiz has fast hands, but once Carnera figures out Ruiz's style, which wouldn't take long I see him moving and jabbing his way to a decision.
You are asking if Carnera can do what AJ failed to do brutally in facing the prime Ruiz? Obviously with his fleet footwork, masterful punch selection, blazing hand speed and showmanship this will end with a Carnera shuffle followed by a volley of countless punches each on a crash course with Ruiz's chin.
It would be similar to Ruiz vs Joshua 1, the only difference would be that Carnera would not offer too much resistance, Ruiz by knockout...
Ruiz wishes. My trainer’s friend Salvador Villa trained Ruiz early in his career and my own trainer even taught Ruiz a few things, so I know first hand how talented Ruiz is, and how dangerous he can be if you punch with him, but I also know how lazy Ruiz is and how movement, turning him, and lighting him up from the shoulder is his krypotnite. I used to see Ruiz get laced up badly at Goossen’s Ten Goose boxing gym whenever they made Ruiz move around and use his legs. Also, Joshua despite his talent is still very green compared to Carnera. I don’t even think Joshua’s had 130 rounds yet.
I never liked the argument that the guy who upset X great fighter, in one fight, beats other great or very good fighters. I tend to expect the great fighter who suffered the loss to own it alone. OK so Andy Ruiz beat Anthony Joshua, but does the rest of his record suggest that he would beat Primo Carnera? Not in my opinion.