This makes a lot of sense, but it didn't work in my case. The front is sitting really high as well. I thought it was just because the motor was still out of it, but I put the motor in and it didn't even sink a little.
With the rear, I took the weight off the springs, removed the rear bushings and greased them up. After putting the shackles back in, I lowered the car down so it had it's weight on the springs, then I tightened everything up. It still sits high. I don't want to do the front again as that's a pretty major operation, and it seems that it's sinking slowly day by day. Any other ideas for the rear?