Mopar Performane valve cover twist on grommet and adapter

The oil cap fill hole that uses the PVC is plugged with a gromet that you'll have to search for. Scroll through the Summitracing web site with known a diamention.

The solid circles are a drill your own. So what ever the item is you want to install, you will need the breather and gromet first before you drill.

Mopar (used to offer? Or still does) offers various items for the valve cover holes, undrilled or the oil capped ones in breather form.

Get the micrometer out and measure up. Convert to inches.
(I know, damn American measuring system!)