PCV systems began being advertised in AD literature (Forward Control Models) prior to 1954 and figure prominently in many 261 applications. They were offered as optional equipment on some models where the truck was used in quick stop/start or delivery service. I have owned two original 1954 (one 261, one 235) versions that had the enclosed draft tube to manifold to valve cover to air cleaner set-up. The 1954 Salesman Data Book lists it as option group 217 for series 3100-6800 in a variety of combinations. The engines section shows the one in my photos on a 261 Series 6000S-6000.
These are some pictures of one from a 1954 235 (2-ton truck).

http://good-times.webshots.com/photo/2040221380102454676LuspIx
http://good-times.webshots.com/photo/2093853490102454676PxCyoF
http://good-times.webshots.com/photo/2915250570102454676yzsJst
http://good-times.webshots.com/photo/2620193000102454676PXNGMi

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr