Just saw the traction bar pic. It didn't show up last time I saw the thread.
If I understand correctly, you are going to get RuffStuff to build a 1/2" diff ring with a tab that you will weld the traction bar straight into. The 1/2" steel construction should mean the load is spread between all of the bolts BUT if you weld the bar into the tab, with no means of pivot, the rod will push / pull on the weld / tab as the suspension travels.
This is not going to work for long. You need some give in the design to accommodate the axle not following the traction bar's arc as the suspension cycles. The accommodation, if not designed in, will happen when shit breaks.
Also...
I haven't seen the Mustang calipers, much less mocked them up next to an XJ knuckle, but it seems to me that the best you can really accomplish with the newer style knuckle is to build a bracket that will tie into 2 of the hub bolts and the two 8mm caliper bolts just for the hell of it. This may be just fine. With a steel bracket... probably is. I think the older style knuckles, with two additional 12mm mounting points, are a better starting place. With 4 12mm threads, you don't have have to wonder. Look at Vanco's big brake kit and trust, just for a moment, that they had their reasons for starting with the older knuckle as a platform to build from.