Don
From what little information I have the Montana hull was to be considerably wider than the Iowa class and would have incorporated an external armor belt. This might have changed its appearance even as a waterline hull. The Montana was to have 4 16" turrets. Had the information become available that the Yamato class battleships had 18" guns it is probable that the Montana would have reverted to an earlier proposed design with 3 18" gun turrets. A trial 18" gun already existed at Dahlgren. It is also possible that with the wider hull the 16" turrets might have also been wider. The Iowa turrets were considerably cramped due to the need to fit them in a hull narrow enough to go through the Panama Canal.
Amphib