I have an '82 series 3 SWB which I am going to swap the leaf springs on. Have a set of standard springs and am currently ordering the smaller parts needed to fit them (shackles, shock bushes etc). The parts manual lists two different U-Bolts one which is flat topped and one which is round. I know the easiest thing to be would be to go and look at the vehicle to see what is currently fitted but it is at home and I want to get the order in as soon as possible so the parts will arrive in time for the weekend. Can any one tell me why there are the differences and which one I would need?