I have one head bolt which will not come off, is now stripped and even the tool made to grab the head of a stripped bolt won't work. It appears to me the next step is an extractor. Any thoughts?

 

Post up some pics. I deal with this dumb stuff daily and there's a whole litany of things to attempt from low impact to destructive. At worse, cut or grind the head of the bolt off and pull the head over the remaining stud. extract the stud with channel locks of a small pipe wrench. Heat at the base of the block will help loosen it if you can get enough focused there.