best to use crown vic brakes if you can find them... there is a write up on JF.
I couldnt find any so I did it the hard way.
You will need TJ rubicon plates. I also recommend gettinga stock d44 one from your XJ.
to use ZJ brakes you need to have backing plates re drilled, as well as the tj rubicon retainer plates. Of course you will need new bearing.seals, and axle collars.
What I did for this way upgrade to chromo's from Alloy Usa since all that came in the kit for 300 (2 yrs ago).
Here is a pic of the axle retainer