Use some allthread, washers, and nuts. Install the allthread and tighten the nuts.Make sure you have a short side and a long side of the allthread. Then remove the allen bolts. When you back off the nut from the all thread do the long side.
The parts must be had thru Eaton. Randy's or 4wheel parts, or any diff shop that carries Eaton products can get the parts. IIRC they are in the $250 range.
When you fix it put it back together the same way. That spring is a bugger without the allthread!