5.0L V8 to 5.7L V8:
* Relatively easier: Both are likely gasoline V8s, meaning the engine bay might already accommodate the larger engine. However, you'll still need to consider:
* Mounting points: The 5.7L may require different engine mounts.
* Exhaust system: A new exhaust system will almost certainly be needed.
* Wiring harness: Significant modifications or a complete harness swap might be required.
* Computer/ECU: You'll need a compatible ECU to control the 5.7L.
* Transmission: The transmission might need to be upgraded or swapped to handle the increased torque of the 5.7L.
5.0L V8 to 6.5L Diesel:
* Significantly more challenging: This swap presents far more obstacles due to the fundamental differences between gasoline and diesel engines:
* Engine bay space: A 6.5L diesel is considerably larger and heavier than a 5.0L V8. The engine bay might not have enough space. Significant modifications to the firewall, body, or even frame might be necessary.
* Fuel system: You'll need a completely new fuel system, including tank, lines, and injection pumps.
* Exhaust system: Diesel exhaust systems are different and often require additional components like Diesel Particulate Filters (DPF).
* Cooling system: Diesel engines often have different cooling requirements.
* Wiring harness and computer/ECU: A complete re-wire and diesel-specific ECU are required.
* Transmission: The existing transmission almost certainly won't be compatible and will need a significant upgrade or replacement capable of handling the torque of the diesel engine. This might necessitate changes to the driveshaft and rear end as well.
* Emissions: The legal aspects of such a swap vary significantly by location. A 6.5L diesel, especially an older model, might not meet current emission standards.
In short: Swapping to a 5.7L V8 is *possible* but still requires significant mechanical expertise and modifications. Swapping to a 6.5L diesel is a *much more complex* project, potentially requiring extensive fabrication and custom engineering. It's best suited for experienced engine swappers with significant fabrication skills and resources. You should research your specific vehicle and the target engine extensively before undertaking either swap.
