In addition to Tony's book, CBCs and the IRM Library as a source for R-40-10 drawings, the Calif. St. RR Museum Library also has R-40-10 drawings available.
Go to :
http://csrrm.crewnoble.com/SearchDrawingsBasic.htm
and enter R-40-10 in the "Description" box.

There is also a link there to contact the library for further info.

Additionally, I have posted prototype photos, prototype data and a few model photos on my SmugMug site:
https://harley-trains.smugmug.com/


Enjoy,
Dick Harley
Laguna Beach, CA