1. Engine Mounts and Frame Modifications:
* Incompatible Mounts: The 454 is significantly larger and heavier than the 350. The existing motor mounts are completely unsuitable. You'll need custom motor mounts fabricated. This often involves modifying the frame or creating new mount structures. This is a critical step requiring precise measurements and welding skills. Consider consulting a professional chassis shop for this.
* Transmission Clearance: The 454's larger dimensions might interfere with the transmission, requiring modification to the transmission crossmember or even a different transmission altogether (depending on which transmission you're using).
2. Transmission:
* Selection: The original transmission might not be strong enough to handle the 454's torque. A stronger transmission, such as a TH400 (three-speed automatic) or a TH700R4 (four-speed automatic), or a heavy-duty manual, will likely be necessary. You'll need to consider the appropriate bellhousing and adapter plates.
3. Exhaust System:
* Custom Fabrication: The 454's exhaust manifolds will be much larger and likely won't fit the existing system. A custom exhaust system will need to be fabricated, potentially requiring clearance work on the frame and body. Headers are generally preferred for better performance and clearance.
4. Cooling System:
* Increased Capacity: The 454 generates significantly more heat. You'll likely need a larger radiator, higher-capacity water pump, and potentially an upgraded fan to keep it cool.
5. Drive Shaft:
* Length: The different engine and transmission combination will require a driveshaft of a different length. You'll likely need a custom-length driveshaft made to ensure proper alignment and avoid vibrations.
6. Wiring Harness:
* Adaptation: The wiring harness from the 350 will not work with the 454. You'll need to either rewire the entire system or adapt the existing harness, which is a complex task requiring a good understanding of automotive electrical systems. A dedicated wiring harness for your specific engine and transmission setup is recommended.
7. Fuel System:
* Fuel Pump and Lines: The 454 will need a fuel pump and lines capable of supplying the increased fuel demand.
8. Other Considerations:
* Hood Clearance: The 454 might not fit under the hood without modifications. You might need a taller hood or significant modifications to the existing hood.
* Weight Distribution: The added weight of the 454 will significantly alter the van's weight distribution, potentially affecting handling and braking.
* Brakes: Upgrading the brakes might be necessary to compensate for the increased vehicle weight.
* Inspection and Registration: Make sure any modifications meet local regulations and will pass inspection.
In summary: This is a highly involved project that should only be attempted by someone with significant mechanical experience and access to welding and fabrication equipment. Professional help is strongly recommended, especially for the engine mounts, exhaust system, and driveshaft. Consider the total cost of parts, labor, and potential unforeseen issues before starting this project. It will be far more expensive and time-consuming than you might initially anticipate.
