OK lemme shoot from the hip here. I researched the swap, had the donor YJ, but never followed thru, sold the YJ, still have the CJ.
If the CJ rear crossmember is still good (not likely), you can cut an offset rectangle around the 2 body mounts, flip them around to effectively move the holes outboard to the YJ width.
I also remember someone on jeepsunlimited was laser cutting and bending his own rear crossmembers with al the correct holes for not much more than a replacement CJ xmbr.
The second to last set of body mounts are slightly different. I can't remember exacyly how to make it work, but I think you just oblong the hole in the tub.
Cut a hole for the CJ fuel filler on passenger side, corner guards to cover the YJ filler.
CJ dash should bolt right in, once the YJ dash is stripped out. Heater box is different, cut/patch holes as necessary.
To make a CJ defrost system work, you'll need to cut ovals in the cowl of the tub. I you're also using a YJ windshield frame, slots are needed here too.
CJ fenders, doors, hood, tops bolt right up. Get rid of the
swingaway hatch and put a tailgate on.
CJ flares will fit, but some holes need to be redrilled.