Lufkin Industries manufactured (still manufactures?) these pumps.
There is a profusely illustrated book- Lufkin, from sawdust to oil : a history of Lufkin Industries, Inc., Lufkin, Texas / by Elaine Jackson ; edited by Virginia R. Allen. Houston : Gulf Pub. Co., Book Division, c1982.
Lufkin was located on Southern Pacific. You might be able to have your local public library borrow this book for you via Interlibrary Loan.
I'm looking for either prototype photos or models of oil field equipment being shipped on flat cars c.1940s/50s. I'm especially interested in a disassembled pump, but anything related would be O.K. Anybody got anything like that?