I just installed 5100’s on the rear of my AT4. Very easy if you pre-plan the shock length. From center to center ( measured from the top Mount to the bottom) the distance is 22”. The Bilstein 5100 come with a band around them that prevent them from being completely expanded. This measures 24 1/4” center to center. What I did was take 4 large zip ties, zipped them together to make a loop , place the shock standing up and put the zip ties on the shock the same manner as the shipping strap. I marked from the bottom of the dust boot 2” with a sharpie, then compressed the shock until the mark lined up to the bottom of the boot. Pulled the zip tie tight, and voilà, had 22” center to center. Attached upper shock mount first, then positioned bottom in its mounting point. Perfect fit, installed the bottom bolt, then righted them. Cut zip ties to remove. Did not have to jack truck up, just laid on my back and used 13/16 sockets, ratchet and pull bars to complete the task. Took 30 minutes to do both sides.I want to do the Bilstein 5100's in addition to the readylift sst kit.