Based on the views of the Nuevo de Julio kit, I would assume that you are right that there are only few modifications necessary to built USS Boise.

For a 1945 fit, you have to add one catapult (the port one). I am not sure about the boats - and some of the light AA guns, e.g. the ones at the bow (20 mm or 40 mm?).

I lack good information about both the late-war Boise and Nuevo de Julio. I only compared the photos on Navsource with the views of the kit.