Nothing I tried was able to get this bolt loose though so I had to go around that problem. Thus I decided to just take off the whole exhaust header.
The exhaust header is supposed to be held on by eleven 9/16 inch head bolts. Five long bolts and six short ones.
My exhaust header was missing one of the short bolts when I got the car, and two of my long bolts had 14mm heads instead of the 9/16 inch heads the rest of the bolts had. I do NOT think that is the way this is supposed to be. I blame the previous owner. :-)