older valve cover - different size PCV?

I put an older valve cover on my engine. the one with the oil fill towards the front of the engine and the PCV opening closer to the firewall. I noticed that the PCV valve opening is bigger. Is there some sort of grommet or is the PCV bigger, or??? Also, do I need to run a line to the air filter or can I just vent it? I have seen some cars with filters attached instead of lines to the air cleaner. Suggestions please.
Michael

umm.....never mind I figured it out. went to the autoparts store and found the PCV grommet.

My 66's valve cover sounds like your current one (called an open system I believe...not same as road draft). There's a grommet at the rear of the valve cover that the pcv fits into (I'd say the diameter of the pcv itself is about the size of a nickel, IIRC) and the line off the pcv runs to a hose fitting on the carb base. The fill cap is a vented type, there are holes on the underside of the cap and a mesh type filter built into the cap; this feeds clean air to the crank case system when the pcv opens and evacuates gases to the carb via a combo of pressure and vacuum (spring in the pcv is strong enough to keep carb vac from opening it, but is over come by crank case pressure at a certain point).

The other style I've seen called a closed system (I hope I'm not mix-matching terminology here).
The main difference on this one is that the fill cap has a line feeding it fresh-filtered air directly from the air breather, but has basically the same configuration on the out flow line of the pcv (ie back to a fitting on the carb body or base).

On the open system some folks run a 'full filter' type filler cap (looks like a mini K&N mounted at the filler). I'm sure it has some performance benefits for high volume oil systems running at high rpms, but might could also benefit other open systems as well

EDIT: whoops Mike...just saw your second post 8)

thanks for the explanation. knowing all of the details never hurts!