The whole inner C and outer knuckle assembly would need to be removed from the CJ axle, and since the CJ & XJ D-30 axle tubes are different diameters (the CJ is bigger than the XJ) you would need to machine a piece of tube to make up the difference between the two, slip it in the axle tube hole on the inner C of the CJ, and weld it to the XJ axle tube. This is just a VERY abrieviated version of what has to be done, so no, it's not as easy as unbolting the hubs from one and swapping them onto the other, if that's what you're asking...