You cold retrofit for a PCV but why? True, emissions are higher with an externally vented engine but there are relatively few of these on the road anymore. If you want to go the PCV route, you need a source of fresh air to the engine and a vacuum source to pull the vapors. Small block chevy's typically have the PCV connected to one valve cover going to a vacumm connection on the carb/intake manifold and a fresh air hose connected from the air filter housing to the other valve cover. You need this "circulation loop" for the concept to work properly. I think someone mentioned putting the PCV valve in the old draft tube location and fresh air to the valve cover. That should work.
