I didn't have the shackle brake on mine, I broke the eye of the leaf. My leaf hopped out past the bushing and shifted my right rear wheel back about 4 inches. This happened when I hit a pothole on a busy road doing 70km/h, My truck nearly went into a fishtail and I nearly hit the car on my left because of it, and to make matters worse, it was a cop car. I pulled into the nearest parking lot, and looked at the damage, and ya, it wasn't as bad as what happened to yours with the bed, but it did chew up the front mount quite good. "New" junkyard leaves (both sides, as the other one the eye broke, but didn't hop out of the bushing). A new front bracket (also junkyard), and I was good to go, I also decided that I would do the shackle flip while I was in there.
I thought I has some bad rust here in Alberta with all the salt they put down on the roads in the winter. I'm going to take a wild guess and say you live in the east. I see that on a lot of the cars I see comign in for Out Of Provence inspections from the east. I don't think I've seen any that bad though. Have fun with your project, and might I suggest (if you arn't already doing so), painting it and then spraying some rubberized undercoating on it. Not fool proof, but its better then nothing.