I had to deal with headstuds broken very close to the case. Normally, the only way to grab those would be to weld a nut on them. But I found an alternative solution that worked very well. I used a nut extraction set from Sears, and I described the procedure in my engine rebuild thread;
Aurel`s engine rebuild thread
They gave up easily with a little heat from a propane torch while applying torque on them.
Aurel