Pat Downs uses stock VW valve covers on his engines.
My engine that Pat built has a breather system that I designed. I have an electric fuel pump so used an aluminum block-off plate where the mechanical pump would've been. I drilled and tapped it for a pipe thread and used -8 stainless hose to connect it to a Porsche oil filter canister which hangs on my fan shroud like the P-cars did. This can is filled with scotchbrite to stop any oil from making it on through the exit hose which goes to the #1&2 side air cleaner.
Haven't had a drop of oil leak from this engine in 5,000 km.