This photo:

http://s142.photobucket.com/user/551stsuburban/media/1955%201st%206400/005_zps3d5a38e6.jpg.html

Shows the PCV valve just after the brass 90deg fitting. Of all the bits and pieces I have when I bought my truck motors I have a draft tube and air cleaner with PCV fittings.

I did read this from the 57 Truck manual in the specifications page:

CRANKCASE VENTILATION
Positive crankcase ventilation on forward control models... vacuum operated closed outlet tube from ventilator body to inlet manifold provides suction when engine is running.
Road draft ventilation on all others.