The Anatomy of the Ship volume on Fuso, which must be available on a used basis from a lot of sources. This probably the best single source reference.

Harder to find would be Gakken volume 30 on the Fuso class. Not better than the AOTS book.

There's also a recent Model Art volume dedicated to IJN BB superstructures, which I could find a link for you if so desired.

A good visual reference is on this link to an utterly superb, 1/100 scratch build of Fuso in her late 1930s-1940 fit by the owner of the Tam Tam hobby shop chain in Japan. Just scroll down past the superb pics of his Akagi build to Fuso. Click on each photo to enlarge it.Great detailing:

http://blog.livedoor.jp/nichirou/archives/54044349.html