1. I would get the u-bolt flip and weld a set of shock tabs to the axle. I did this on my 4 Runner, works fine.
2. You can reuse the stock ones and tack them to the u-bolt flip plate, or pick up a set of universal bumpstops, ebay has them often, and mount them to the bracket that hangs down from the frame. This is how mine are mounted.
3. Those are to hold the springs if too much weight is put in teh bed, I wouldn't worry too much about them.
4. For brake parts, check out Rock Auto online. They usually have great pricing and all the parts needed.
DD - 05 Toyota 4 Runner
Trail Rig - 88 4 Runner with dual cases w/ 4.7's, 37" PB Rockers and no lift
99' Toyota Tacoma Crushed by Toyota