* Engine Mounts: The 460 and the 6.9L have completely different engine mount locations. You'd need custom engine mounts fabricated, which is a complex and potentially expensive undertaking.
* Transmission: The 6.9L likely came with a different transmission than a 460 would use. You'd need to swap the transmission, driveshaft, and possibly the rear axle gearing to match the 460's power and torque characteristics. This is a major undertaking.
* Wiring Harness: The electrical systems are vastly different. You'd need a complete custom wiring harness to handle the 460's ignition, sensors, and other electrical components.
* Exhaust System: The exhaust system will need to be completely redesigned and fabricated.
* Cooling System: The 460 will have different cooling requirements than the 6.9L. The radiator, hoses, and potentially the water pump may need to be changed.
* Fuel System: You'll need a complete gasoline fuel system, including tank, lines, pump, and injectors.
* Computer Control: The 460 may require a different computer control system, potentially requiring further custom work.
While technically possible with significant fabrication and mechanical expertise, it's a massive and very expensive project that's far beyond a simple swap. The cost and effort involved would likely far exceed the value of the finished vehicle. It would be much simpler and cheaper to find an F-350 that originally came with a gasoline engine if that's what you prefer.
