if you have access to a welder, weld a large nut on the remainder of the
stud.  this generally gets the stud hot like a torch would.  when the weld
cools begin taking the stud out as you would any frozen bolt, lots of
tapping with your favorite hammer and liberal application of penetrating
oil.  if it still doesn't want to come out you might have to heat it a bit
more with a torch, but be careful not to over heat the alloy.

jonathan