I did just what Rick did,first tap was too "tight",then got an old rusty one and cut some threads of after cleaning it up and re-tapped the holes,you will have to go in till the tap bottoms out on the cylinder wall,sometimes hard to "feel" so I backed it 2 or 3 times to check the cylinder wall..................
BTW: You can still buy the original type screw-in freeze plugs from Ford Motorsports for about 12 to 15 bucks per block.........
Look in my gallery,that's a plain jane 1971 302 block,looks just like a Boss block though............
Only reason I tapped mine was when I took the engine down to have machined,the machinest told me two of the freeze plug holes had a lot of pitting on the edges and thought they would surely leak with use,so we tapped them cause at the time,that was the only good block I had,total cost about 20 bucks............
David
