Get some Dick Cepek Extreme country or Mickey Thompson MTZ tires. I loved the DC tires on my XJ.
p.s. I had the Nitto Mud Grappler tires on my old Jeep and they wore out quick and were really loud.
Thats a sweet looking XJ. I thought about the DC Extreme Country tires, but couldn't find many reviews on them. I did end up going with the MTZ's, which I do like, but they are noisy at hwy speeds.