Yeah, I understand that they'll never be the same. It just seemed that if all of the wiring from the motor and ECU on the XJ is used on the CJ, it would just be a matter of bolting it in correctly.
Imagine this...
Remove all of the drivetrain and electrical parts (including the dash) from an XJ and put them on a frame (any frame that they'll fit on). The guages and other instruments will still work the same since they are all connected to the same wires only now they're in a different spot.

I find that I have a knack for oversimplification. This is perhaps just another case of that!