Dartin for Divorce

Doc - several different options, check a few things first

for the holes that are not open, check to see if it is a knockout plug

the cap you have in the picture may or may not work but there should be one that would work similar - keep shopping

check the help sections at azone/oreilly's, they generally have a couple different grommet sizes for the valve covers, one with a larger hole for a cap and one with a smaller hole for a PCV directly, also the overall grommet is available in different sizes, may also be a grommet list for a brake boosted that will work