Put the head back on with the remaining bolts, a little more than hand tight.

Look in mcmaster carr, or msc catalog, and find a drill jig bushing that has an od the size of the hole in the head.

buy a long carbide center drill, and using the head and bushing to center the drill, drill a pilot hole in the old cyl bolt.

Once you have this done open the hole to correct size for extractor.

John C.