* Engine Mounts: The engine mounts are almost certainly different. The J-series truck frame and the Grand Wagoneer's unibody will have different mounting points. You'll need to fabricate new motor mounts or adapt existing ones.
* Transmission: The transmissions might not be compatible. You'll need to ensure the transmission from the J-series truck works with the Grand Wagoneer's transfer case and drivetrain. This might involve adapting bell housings or using an entirely different transmission.
* Wiring Harness: The wiring harnesses are different. You'll need to either extensively modify the J-series harness to work with the Grand Wagoneer's system, or possibly use a harness from a similar-year Grand Wagoneer with a 360. This is a complex task.
* Exhaust System: The exhaust system will need to be custom-fabricated to fit the new engine and Grand Wagoneer's body.
* Computer Controls (Possibly): While both are likely to be carburetted, the 1990 model *might* have some electronic components related to emissions that won't be compatible with the older engine's setup. This is less likely than the other challenges, but still a possibility.
* Radiator and Cooling System: The radiator and associated components might not be directly compatible, requiring alterations or replacements.
* Steering: The steering linkage might interfere with the engine or require adjustments.
In short, this swap is a major undertaking requiring significant mechanical skills, fabrication expertise (welding, etc.), and access to specialized tools. It's not a weekend project. Unless you're experienced with engine swaps and modifications, it's best to seek the assistance of a qualified mechanic specializing in AMC vehicles and older Jeeps. Simply put, while the engines are the same displacement, the surrounding systems are significantly different.
