Here's what you need to consider:
* Motor Mounts: The location and style of motor mounts changed over the years. You'll almost certainly need to adapt or replace the motor mounts.
* Bellhousing: The bellhousing (connecting the engine to the transmission) may not be compatible. The bolt pattern on the 454 block might differ from the 396's, requiring a different bellhousing.
* Transmission: Make sure your transmission is compatible with the 454. A 396 might have been paired with a transmission that won't work with a 454.
* Accessories: The placement of accessories like the alternator, power steering pump, and air cleaner may differ, requiring modification or the use of different accessories.
* Exhaust: The exhaust system will almost certainly need to be modified or replaced.
* Wiring Harness: The wiring harness may need to be altered or replaced to accommodate the 454.
In short, while it's *possible* to swap a 1979 454 into a 1969 Chevy truck, it's not a simple bolt-in affair. It will require considerable mechanical knowledge, fabrication skills, and potentially many replacement parts. You're looking at a significant project, not a simple swap. A professional mechanic specializing in classic Chevy trucks would be best equipped to assess the feasibility and cost.
