Blow By

PCV on a 65 Dodge was just a mild vacuum source for the crankcase to promote a constant ventilation of oil vapor into the carb base to prevent sudge and moisture condensation. The oil filler was a slip fit cap with a brillow pad filter in it. I dont think a plugged or lack of PCV on a 65 would cause blowby control issues as its already vented to atmosphere through this large opening. Also the umbrella valve seals are probably long gone and are already in the oil pan as black plastic gravel.