* Mounting: The Cummins 5.9L has a different engine block, bellhousing pattern, and overall dimensions. You'll need custom motor mounts and potentially significant frame modifications to fit it properly.
* Transmission: The transmission used with the 7.3L IDI likely won't bolt up to the Cummins. You'll need a compatible transmission (likely a different transmission entirely) and associated adapter plates or a custom driveshaft.
* Wiring Harness: The electrical systems are completely different. You'll need a new wiring harness tailored to the Cummins engine or extensive rewiring.
* Fuel System: The Cummins has its own fuel system requirements (fuel tank, lines, filters). You'll need to adapt the existing fuel system or install a new one.
* Exhaust System: The exhaust system will need to be completely replaced or heavily modified to accommodate the Cummins.
* Cooling System: The cooling system may also require significant changes to fit the Cummins' requirements.
* Computer/ECU: The Cummins engine uses its own computer, and the integration with the truck's systems will be a major hurdle.
In short, this is not a weekend project. It's a major engine swap requiring significant mechanical expertise, fabrication skills (welding, cutting, etc.), and access to specialized tools and parts. The cost could easily exceed the value of the truck if not done carefully. Unless you have extensive experience with this type of work, it's strongly recommended to seek professional help from a qualified mechanic experienced in heavy-duty engine swaps.
