None of the steering linkage on an XJ mounts to the frame, except for the pitman arm on the steering box, which in turn is mounted to the frame. Are you sure you are not confusing the Track Bar with part of the steering linkage?
In any case, NONE of the various rod end joints in the steering linkage (or on the end of the track bar where it connects to the chassis) should have ANY play in them.
If they do, it's time to replace them.