Yup, you're going to have to do a bit of enlarging on the holes with the bigger ratio, at least on most of the old OEM heads things got a bit too tight.

Are you running the engine under a class rule that requires stock height covers??? We had to do the same thing back a decade or so ago. The rules said you had to have stock height covers, but they didn't say a ting about running valve cover spacers under the stock height covers! Had plenty of room for big rockers.....