seems like a lot to go thru when you can put a soft plug in the old tube hole(brass) so it won't leak, and run a set of late model valve covers...
What everybody is skirting around is that if you pull your pvc side with vaccum- then you need a cross vent from the other side to allow it to pull thru the crankcase, instead of FROM the crankcase.
Like I said........vent the other valve cover, you can get a vented cap for oil that will fit right in the knock-out, or you can just get one that already has one & bolt it on.
OR you can do what Ed did- that looks pretty sweet & clean.
I used Eldebrock covers on mine & they come with vent caps.