On my '84 Scrambler - I just installed front/rear MORE shackles - there's an extra bolt w/sleeve for each shackle set, which I first thought to be the hanger/bolt for the other side of each set of springs (and couldn't figure out what the sleeve was for).
Then it came to me that the sleeve would fit in the middle hole of the bracket and tried it on the rear - but it doesn't seem needed (steel's already thicker than the stock, and it causes a little bulging in the center as the bushing is just an 1/8 inch or so too long.
Thanks in advance...if anybody's interested - the shackles went on w/ out a problem (old & original were a bear to take out). Ride much improved.