Things that are likely interchangeable:
* The engine block itself: The basic block is very similar, if not identical, between these years.
Things that *might* require modifications or are less likely to be directly interchangeable:
* Computer (ECU): The engine control units (ECUs) are likely different due to emission standards and possibly slight variations in engine calibrations. Swapping the ECU will probably require additional wiring changes to match the sensor configurations.
* Wiring harnesses: While the basic connectors *might* be similar, the harness routing and specific sensor locations could vary enough to require significant modification.
* Exhaust Manifold: Minor variations are possible, preventing a direct bolt-on.
* Sensors: Though the same sensors are *likely* used, small differences in the connectors or sensor bodies could cause issues.
* Accessories: Alternators, power steering pumps, and other accessories might have different mounting points or pulley sizes.
In short: You can *probably* swap the long block (engine block, heads, and internals) but expect to spend considerable time addressing the peripherals. It's not a simple plug-and-play swap. You'll likely need to use the wiring harness, computer, and other accessories from the donor vehicle (the 1998 Grand Cherokee if that's what's being swapped in). Even then, you may encounter minor incompatibilities. Researching the specific part numbers for the engine components and accessories would be prudent before attempting a swap.
