Good post, above.
If you do go with valve covers with only ONE hole per cover....... one hole is used for the PCV and the other hole is for a breather or vent pipe........ and no filler cap. You would remove the breather or vent pipe from the valve cover to add oil.
Also, the hole for the PCV valve should have a simple metal deflector below it. This prevents oil from splashing directly on to the PCV valve itself.
BTW..... do NOT do what my buddy did on his Chevy 350 V8. He used a PCV valve only, and plugged the other two holes with rubber oil filler caps........ no vents at all. Since the PCV valve is too small to vent crankcase pressure under heavy throttle, he blew out all his crank oil seals.
