73 340 Compression Test interpretation help

You will want to put the PCV valve in the valve cover opposite the breather inlet. Which will be the left side based on the pictures you posted. Buy a regular Mopar style PCV valve and grommet, and measure the grommet to see what size hole you need to make in the valve cover. A low buck hole saw will cut the aluminum just fine. Remove the valve cover and drill from the back.