While you'll probably find some people here experienced with normal Carbs, I wouldn't expect anyone to know about the electronically controlled carb in the XJ.
I could only help with the TBI or MPI system (even then, to a limited extent). All I know is that alot of people simply strip ALL of the electronic control, plug the EGR stuff, and put a standard carb on instead. Usually they'll get alot more power, with similar gas mileage (bad either way, haha), but it'll be tricky, I'm sure...
I've seen water heated two barrel carb accepting intake manifolds, as well as plenty of two barrel carbs to match, but don't know many details there...
Either way, good luck!