1971 (1979) would be closer to the time of the "new image" modern feather logo. (which, imo, sucks)
Sometime in the mid 70s, they revivied the classic logo and placed it on a few boxcars
and one covered hopper (like Micro Trains has done).
The classic WP hearld goes way back to......20s or 30s ? (Railroad started in 1903?)
The original logo just had the feather going into a circle that said "Feather River Route",
the the words WESTERN PACIFIC were added around that to create what most people know.
This tells more about it, but my not be 100% correct, imo.
http://www.wplives.com/history/herald_history/index.html