As long as the drilled hole is in the water jacket.

My 261 has the original PCV valve that screws into the draft tube. The draft tube has a oil mist collector inside.
The other end of the PCV valve has a metal pipe (~5/8") going to a hex brass fitting on the intake manifold.
Air cleaner to valve cover has 5/8" rubber hose. The diameter of the hose and pipe is important to get the proper flow through the PCV valve.
The valve operation can be checked. It can also be disassembled (unscrewed) for cleaning.
The engine picture is my original 261 with the intake removed to fix damper valve.

Just curious. Are you running the original 261 Rochester B? Mine (7015013) ran rich.
Attachments
261 Head 02.jpg (33.23 KB, 206 downloads)
Ports 01.jpg (329.59 KB, 207 downloads)

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."