Interesting fight from a freakshow perspective. Height difference would be eight inches or so. Maybe Primo by decision.
Galento could hit like a hammer. At his best he was a feared hwt for his ko power. I could see Primo at his best out pointing Two ton or just as possibly Galento scoring a KO.
Granted, Galento had a wicked left hook, but, you could knock Primo down, but he was a hard man to keep down. Not sure about Galento's stamina and his ability to go the full 15.
Reach and mobility too much in Primo's favor here. Even Paul Gallico admitted one could hammer his body all day with no effect. Any stoppage would be by Carnera on cuts. Tony wouldn't have been able to butt or elbow Primo much, and when it came to rough stuff at close quarters, Carnera was no choir boy either. If the conclusion was a DQ, it would go against Two-Ton for a low blow, maybe the only foul tactic available for him to attempt. (They did wrestle a few times after leaving boxing.)
I think Primo is quite capable of getting a decision here, but he might run into a left hook that makes score cards academic.
My pick is Primo by decision. His boxing skills were sound and I believe his chin is underrated. It took Max Baer 11 rounds and just as many knockdowns to stop him in a rough and tumble battle. Two ton might score a KD, but as was mentioned earlier, a hard one to keep down.