Might as well add more fuel to the fire while we wait on the response from the OP.
Correction. 1964-66 for California Emissions.
The thing is, a PCV system doesn't work well if there are other sources of outside air leaking in (valve cover, lifter galley cover, timing gear cover, oil pan cover, etc.). AC Spark Plug Division of GM created testers to check for leaks. Today the issues with installing a PCV system on older engines becomes involved because it is a vehicle specific metering system and the original engineered parts are no longer made. The other headache is that our older engines are expensive to rebuild and they are still being used as is. Blow-by gasses and excessive oil mist renders the PCV valve with a "sticky" problem.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
