Devin:
I built the Monogram version of the kit about ten years ago and it is still one of the nicest builds I've ever done. The fit of the parts was still great and there was hardly any flash.
I did a lot of research on the Susquehana, sadly Imai produced a configuration that may have existed only for a very short period of time following her commissioning with a main armament of sixteen 8" smoothbores, all on broadside, and this may have been her fit when she was part of Commodore Dewey's squadron in Japan in 1853 (which would be logical for Imai).
According to most sources (including Caney's book), the Susquehana and her near-sister Powhattan, had two 10" smoothbores on pivot rails on the bow and eight 8" smoothbores in broadside (4 per side) aft of the paddlewheels. During the Civil War, her armament was significantly increased with 9" Dahlgrens in broadside and heavier guns (150 pounder Parrot rifles on pivots).
I couldn't find 150 pounder Parrot rifles and pivot carriages in 1:144, so purchased 9" Dahlgrens and 100 pounder Parrots from Model Shipways and put fourteen Dahlgrens in broadside (7 on each side of the ship), Parrot rifles in the forwardmost gun ports, and a Parrot on the poop in a scratchbuilt pivot carriage. You may have better luck with commercial fittings now, I haven't worked in that scale in a while, so not sure if there have been some new offerings.
Good luck, it's a great kit!
Mike