Will test the vacuum at the port tonight. There are aftermarket valve covers on the engine at the moment. Oil filler cap is on the passenger side, no opening on the driver's side. Engine was dry as a bone when the PCV was hooked up to manifold vacuum, so I believe the culprit is the carb port. I'll test to make sure.
68 400 convertible - recent purchase
Used to own: 69 400 convertible - Winward Blue 69 350 convertible - Verdoro Green 69 350 coupe - Matador Red