Thanks for all the suggestions. I tried them all except the acetone soak overnight. I have a poor man's brazing torch that uses one tank of Mapp gas and another tank of oxygen. I was able to get it red hot while still on the car. I had wet rags, water, fire extinguisher at the ready. It burned out the grease and rubber bushing fairly quickly.
James was correct in that the tool I bought from a vendor specifically for the plug was the first item to break. It still wouldn't come out, so it became a matter of will power between me and the drag link plug.
Next I took the double ball steering arm the drag link attaches to off the PU. I had already removed the tie rod end to rebuild it anyway, so what the heck. Of course the cotter pin holding the steering arm got stubborn, so off came the wheel as I was going to check the brakes and grease the wheel bearings anyway! I had to pull the backing plate to get at the cotter pin, so off came the backing plate. So now I get the drag link and steering arm in my vice for some real action. I heated it to red hot again, but still no movement so I put more rust remover in the link and let it sit overnight upright with the plug end full of the stuff. This morning it had all leaked through, so I started tapping lightly with a hammer. Still wouldn't come off, so I got my sawzall and cut a section out of the drag link, being very careful not to mess up the ball on the steering arm.
I ruined the drag link, but saved the steering arm. With one section removed, the plug backed right out. I think the problem was one of the prior "owners" was a gorilla, and had tightened the plug as much as he could against the ball. I've found some other evidence of the same tactics on the PU.
Again, thanks everyone for the suggestions. I'm sure I'll have a chance to try them again as I dive into the mechanics on this beast.
