...4 cylinder engines. A grommet for a standard size valve cover breather, a nipple that takes a manifold vacuum hose, and a tube to the air cleaner makes the whole set-up. The nipple has a breather screen inside. I have been using this PCV system for years with some unmolested "Thunderbird" valve covers with my Streetmaster, and M/T Power Ram.
E-Mail me if your interested in piece'n together a set-up like this. I think I still have some of this "junk" lay'n 'round.
Kinda hard to see in the pics...and that's the idea! You can also use the hole you drill in the back of the manifold for the nipple to use as the oil-fill for the engine.