I have the same valve covers but didn't have to do any drilling, they were already drilled out when I got them.

I use the Mopar twist on oil/breather cap, kills two birds with one stone and no problems. $7.99 most anywhere where they sell mopar supplies. It's not to unusual to see that being used along with a seperate push in breather, especially on high performance engines. I haven't done it yet but plan on it. Let me know how your drilling comes out.