Damn the bad luck

I like the welded nut trick, I may try that. The left hand bit, I don't know, the other studs I took out were pretty set in there. But I may buy one anyway. I'll have to pull the motor/trans out on Friday and go to work on it. If I get lucky and drill in the center with a 1/4" or 9/ 32" bit I may be able to use a 5/16-18 tap and push the old part of the stud inside. Then I can knock out the freeze plug out in the end of the head and remove the pieces.Thanks for all the help