I prefer this solution to the frozen/rusted/seized/broken upper rear shock nut/bolt.
After you remove the shock weld nuts with a punch, you can feed replacement bolts in from above by fishing them through the cross member with a wire attached to a piece of string, taped to a new bolt.
Then you can slide your open end wrench into the cross member and onto the head of the bolt, while you tighten the new shock retaining nut from below.
Also, this......
http://www.naxja.net/forum/showthread.php?t=913774&page=14