Couple options:
- EZ- Out (not likely but worth quick try if you already have in tool chest)
- Weld hex nuts on and use socket or box wrench
- Cut slots in head w Dremel converting into flathead
- Dremel cut heads off completely - better access for remaining stud removal once out.
No matter path you choose... go very slow and be really careful to protect the paint so it doesn't get buggered up more.
Good luck
