This needs two sets of hands as you need to align the wishbones pretty well on both sides as the tolerance is tight. You need to ensure that the thrust bearings on either side of the bearings remain in position. I found that it helped the grease the bearings well so they stuck together. I also used the lower shock shaft to hold the bearings in place whilst I pushed the full shaft through from the other side. This is a bit fiddly so having an extra set of hands were needed. I used the original inner fulcrum shaft as it was in good order but I used new nylon nuts.
One I had both sides attached I could fit the remaining brackets from the kit to attach the IRS assembly to the chassis. This was harder than it sounds as you need to man handle the diff, brakes and now wishbones to get access to the fixings under the diff brackets. Again having my son help me here was invaluable. We found that the holes in the bottom plate did not align completely perfectly so getting the bolts to fit the thread was a little problematic. With patience we finally made it and did not resort to drilling out the holes, which had crossed my mind in frustration!