I did a write up on this a while ago -
Go to Search -> Advanced Search -> Search Titles Only and type in
Oil gallery modifications performer heads - the pix will show you exactly what this is all about.
The plugs are available from umm.....the guy in CA who blueprints the Melling pumps - I forget his name right now, but I have it at home - email me if you want it. He has different sizes of center holes, depending on your objectives.
You can't do it on the car due to the metal filings the tapping process creates.
Good luck, B
