* Engine Mounts: The engine mounts from the 1978 truck likely won't directly fit the 1984 frame. You'll probably need custom motor mounts or mounts from a similar-year truck with a 351M.
* Transmission: You'll need to ensure the transmission from the 1978 truck (or a compatible one) is compatible with both the 351M and the 1984 truck's drivetrain. The bellhousing bolt pattern might differ, requiring an adapter or a different transmission.
* Wiring Harness: The wiring harness from the 1978 truck will likely need significant modification or replacement to work with the 1984 truck's electrical system.
* Exhaust System: The exhaust system from the 1978 truck probably won't fit the 1984 truck. You'll need a new exhaust system fabricated or adapted.
* Computer Control (if applicable): The 1978 351M might be carbureted, while the 1984 truck may have electronic fuel injection or a different emission control system. This will significantly impact the swap. A carbureted setup would be simpler, but might not meet modern emission regulations.
* Accessories: The power steering pump, alternator, and other accessories may require adaptation or replacement to fit the 1984 truck.
In short, while it's *possible*, this is not a simple bolt-in swap. It's a significant project requiring mechanical expertise, fabrication skills, and potentially significant parts sourcing. You should have a good understanding of automotive mechanics before attempting this. Consider consulting with experienced mechanics or searching for forums and resources specifically on this type of engine swap for more detailed information.
