The 1950 Locomotive Cyclopedia has a set of prints, and some nice detail shots of the tender connections.
Also some great additional Niagara technical articles may be found here:
https://nycshs.files.wordpress...he-niagara-story.pdf
https://nycshs.files.wordpress...016/01/niagara21.pdf
https://nycshs.files.wordpress...dtestingniagaras.pdf