* Engine Bay Differences: The SRT-4's engine bay is likely reinforced and designed specifically for the larger, more powerful engine and its associated components. The SXT's bay isn't built for that. You'd likely need significant fabrication work to make it fit.
* Transmission Compatibility: The SRT-4's transmission (likely a manual) is not directly compatible with the SXT's transmission mount points and drivetrain. A new transmission and associated components would be required.
* Wiring Harness: The SRT-4's engine control unit (ECU) and wiring harness are completely different. Adapting this would be a major electrical undertaking.
* Suspension and Braking: The SRT-4's suspension and braking systems are significantly upgraded to handle the increased power. You'd likely need to upgrade the SXT's systems to safely handle the SRT-4 engine.
* Cooling System: The SRT-4's cooling system is designed for a much hotter-running engine. You'd need to upgrade the SXT's radiator, hoses, and potentially other components.
In short, while it's *theoretically* possible with immense effort and expense, it's not a practical swap. The cost and complexity would far exceed the value of the resulting vehicle. It would be far easier and cheaper to find a different car with the SRT-4 engine already installed.