twist on breathers with PCV valve?

Here's the problem. I have a set of nice old aluminum valve covers I would like to use on my 350, but the problem is they only have holes for twist on style breathers (not push-in style with the rubber grommets). I'm trying to figure a way to set up a PCV valve to work with these covers. I would like to run a breather on one side and PCV on the othere. I don't really want to drill another hole in them. Are there any solutions out there?

Sure, both Ford and MOPAR used twist in caps with with a hole in the top and a grommet for the PVC valve.

Aftermarket versions seem to be a little harder to find now, but they are still around. A "get me by" solution would be to pick up the PCV cap amd a plain vented cap at a wrecking yard (look for cars in the late 60's late 70's).

Thanks for the info. Come to think of it, I remember seeing caps like that. Does anyone out there have one they want to part with?