With Calzaghe fighting as a Lt. Heavy now and Floyd in actuality being a natural Lt. Heavy I think Calzaghe could pull it off. With his high volume punching style and his demonstrating he could take a Lt. Heavys punches I like his chances.
floyd would blow calzaghe away in three rounds max. joe doesn't have the firepower to take advantage of any chin weakness floyd may have had and floyd has the speed to blow his speedy lighter opponent away. floyd's firepower is going to be like nothing joe has ever felt. joe is vulnerable but with immense recuperative powers and balls of steel but he would be outgunned and early.
Floyd Patterson would obliterate him if he gets caught cold in the first round. Patterson hits harder then anyone Calzaghe ever fought, and by quite a wide margin. If he hits him, it's going to be over, better believe that.