* Engine Mounts: The engine mounts will likely need to be modified or replaced to accommodate the 454. The 1968 truck was likely designed for smaller engines. You might need custom mounts or mounts from a later-model truck that used a big-block.
* Transmission: The transmission needs to be compatible with the 454's torque. A heavier-duty transmission from a truck that came with a big-block would be necessary. You'll need to consider the bellhousing and drivetrain compatibility.
* Exhaust System: A new exhaust system will be required to fit the larger engine.
* Steering: The larger engine may affect steering clearance, possibly requiring modifications.
* Radiator: A larger radiator will likely be needed to handle the increased cooling demands of the 454.
* Wiring Harness: The wiring harness may need to be adapted or replaced to accommodate the 454's electrical needs.
* Frame Reinforcement: The frame might benefit from reinforcement, especially if you intend to use the truck for anything more than light-duty driving. The extra weight and torque of the 454 put extra strain on the frame.
* Brakes: Upgraded brakes may be necessary for improved stopping power, given the heavier engine.
In short, while it's feasible, it's a significant undertaking requiring mechanical knowledge, fabrication skills, and potentially a substantial investment in parts. It's not a weekend project. You'll likely need to consult with experienced mechanics or hot-rodders who have undertaken similar conversions.
