David,
I can appreciate your desire to reproduce the K27 in as close to the prototype standards as possible. Don't let the lack of drawings be a stumbling block. The typical observer of your locomotive won't know and won't care how you built the unseen components of your locomotive. I'm building the C&O Greebrier (4-8-4) #614 in 7.5" gauge/1.6" scale and I'm definitely not trying to fully reproduce every single part. What you and I are building, while they are miniature reproductions, are new prototype models in and of themselves.
Just some food for thought. Keep going and don't lose steam!
Rob Gardner