As posted by Brad:
A PCV type of "ventilation" system was first used as standard equipment by Chevrolet in 1948 on the model 3742, a Forward Control Delivery Chassis, updraft carburetor: crankcase ventilation: "closed system, vacuum operated" (1949 description). This was not available on COEs (standard or optional) at that time.
Positive Crankcase Ventilation (by that name) was an option on COEs and some/most standard-cab large Chevrolet trucks by 1953.
In 1954, PCV was optional on all sizes of trucks with either the 235 engine or on trucks that could have the optional 261 engine. In 1954, the 261 engine was an option only on 1.5 and 2.0 ton trucks; and, the PCV option was a separate option (not necessarily installed with the 261 engine option).
