Bernhard, Yes the coil spring bars do have the instructions and hardware. I can post up some pics when I get a chance.
Sam, Those are some great pictures! That helps a lot. There is not a lot of info on these bars. I am assuming the snubber has a slot in it for the retaining bar? It looks like it would be pretty easy to make, if you could find the rubber.
rszmjt, The square tube bars were never on a car. You can see the part number imbedded in the paint on one. Its pretty hard to read but the part number is 3996323 (GM a body axle snubber)
Scott