Finally I drilled the bolt out and inserted an easy-out. But it just had the square end on it & I needed something to put a breaker bar on. A large 1/2" drive Torx went on backwards, then some kind of stripped nut remover hex bit (I think) over that, which gave me something to put the socket on . That sucker was in there tight! I was leaning on the breaker bar chanting at teh easy-out, "Don't break, don't breeeeaaaak!" Finally it broke free.