MP valve covers knock out machined for pcv grommet (Chevy style)

I believe this is what would have worked for you if the breather (or whatever) requires a 3/4" hole. I have personally confirmed this on my own MP cast valve covers - perfect fit (replacing the MP PCV grommet):

Ford Performance Parts Valve Cover Grommet Sets M-6892-F

fms-m-6892-f_w_ml.jpg

My photo below. MP and Ford grommets are dimensionally the same except for center hole:

1-2-Mopar-and-3-4-Ford-grommets-Ford-Performance-Parts-M-6892-F-20184423305165.jpg

Nice machine work, though!