Finally got the upper right rear shackle bolt out. Pardon my misuse of the proper terms. I hope this description is understandable.
To say that the shackle bolt was tight is an understatement. The first thing that gave way were the welds that held the shackle bolt "body" into the hanger. After that I had to use a small monkey wrench on the shackle body to hold it will I tried to loosen the bolt. Then I broke my 12 point 7/8" socket. I went to a 6-point socket, with a 2 foot breaker bar, and turned the corners off the bolt head. Then had nothing to lose, so I put a 3 foot pipe wrench on it, and turned half the head off. By then I was figuring that I would end up cutting the hanger off, and putting a new one on, a job I was not looking forward to. But I was not ready to give up. I took a 2 pound sledge hammer and beat the hanger open so that I could get the shackle body out. After I got it out, I put was was left of the bolt head in my vise, heated the body with my little propane torch, put the big monkey wrench on it, and broke the rest of the bolt head off. You could now look right thru the body where the shackle screws in, and I figured I was done. I got my cutting wheel ready to cut the hanger off, but had one more option. I called my welding expert, and took what I had left over to him to see what he could do. He was making no guarantees. He took a 5" bolt that fit snuggly inside where the shackle screws in, and gas welded it to what was left of the bolt head, and to the other end that protrudes. He put it in a huge vise, turned on the welded bolt, and BROKE THE WELDS trying to unscrew the stuck bolt. Then he arc welded the bolt back on, and broke THOSE welds. I had never seen anything like this. He said there was one more thing to try. He re-arc welded the bolt in, and heated the body until it was tangerine orange, turned on the bolt he had welded in, and finally the shackle bolt came out. Unbelieveable.
I took the part back home, put it back in the hanger, bent the hanger back into shape, welded the part in with my little Hobart welder. And, easy peasy Japanesee, I was done! Only took me 6 hours, over the course of 2 days to remove one shackle bolt. Happily both shackle bolts came loose easily on the other rear spring.