Here you can see details of the front spring plate. When you put the YJ springs on, you cannot use the original CJ spring plate (YJ springs are wider and the U bolt holes do not line up).
For the rear you can re-use the CJ spring plates since CJ rear springs are the same width as YJ rear springs. You cannot use rear CJ spring plates on the front either since the U bolt holes do not line up (mostly due to the extra-wide U bolt on the drivers side).
All of this means that you need to fabricate some springs plates from scratch. I went and got some 4mm plate cut to the correct size. I drilled the holes and used my shop press to hold the plate with about 12ton of pressure (press was acting like a big vice). I then used a sledge hammer to put the fold on the edge. This was another big job.
I then cut the shock and stabiliser mounts off of the original CJ spring plates and re-welded them onto my new spring plates.
Here is the XJ power steering box mounted on the CJ brackets. I only had to make one minor modification to the manual steering box brackets to allow the power steering box to mount up. I had to cut a small rib off of the stock brackets to clear the power steering box. This cut makes the brackets look exactly like the stock power steering brackets. I used a mix of XJ and TJ power steer hose pipes to route the hoses up to the pump.