The manuals on foundation brake rigging, air brake and signal lines (for passenger trains) car brake inspection and K- brakes would pertain to the NG. Although he NG did not interchange, where applicable, they would use the AAR manuals. The NG didn't get into hauling hazardous materials much, although I bet hauling pipe in gons with the ends knocked out of them would be fowned on in the steel handling book.
Any ICS book is a good find and applies to just about any old railroad. SG or NG.
Good find, I learned a lot reading old ICS, WABCO, etc manuals.