I picked up some engines not too long ago and two of them had head studs broken flush with the block. I used the "TIG method" that Vince Falter shows on his web page
http://www.fordgarage.com/pages/studremoval.htm The first engine had four broken studs and the weld broke on all of them the first time I tried. I welded again and two came out, the next time number 3 came out and the fourth attempt, the last one came out. The threads are nice and clean. This method worked great. I spoke to another member of the club and he MIG welded a bolt to the stud to get his out.