The turbo oil seal was leaking on my 1991 350 SD. Turbo and manifold was removed and I discovered the exhaust stud nearest the firewall was broken off about 3mm below the surface. I can't seem to remove the stud with a screw extractor. There's a 1/8" hole drilled into the center of the broken stud and the stud actually rotated and bottomed into the tapped hole while drilling with a right handed bit. Now I think removing the head is my only option. Can someone provide instructions (or a link) to remove and replace the head?

Thanks in advance.

Greg