On an XJ, you'd really need to get some solid mounts like the way tow hooks are bolted on.
There's a good amount of stress on the brackets when tow bar-ing. Had one snap off the frame on my CJ-3a when we were mowing it, that wasn't fun.
BTW, do you still need a tow bar? I have one on there flattie, I think its a 5000lb universal draw tite.. I'd have to go get it(the jeeps in the barn near Lapeer) but I don't need it anymore...