If you're contemplating swapping MJ axle shafts into a CV-shafted XJ axle, then you've got one minor dilemma. The CV axle will not have a CAD. Almost all MJ axles are of the CAD variety and the passenger side axle shaft will be a 2-piece unit and can't go into a non-CAD axle. You'll need a shaft from a non-CAD front axle. You might as well focus your efforts on some axle shafts that use the bigger 297 U-joints as they will be stronger. TJs, 96+ XJs, and older XJs that had ABS will have the proper shafts/joints.
And yes, the axle shafts will always and only go with the type of joint they were made for. The yokes on the ends of the shafts will only connect to the proper joint, whether CV or 260 U-joint or 297 U-joint. :thumbsup: