* Engine Mounts: The engine mounts on a 1985 Chevy engine will almost certainly not line up with the frame mounts of a 1975 Chevy truck. You'd need custom mounts fabricated.
* Transmission: The transmission from the 1985 engine may not bolt directly to the 1975 truck's transmission. You might need an adapter or a complete transmission swap.
* Wiring Harness: The 1985 engine will have a completely different wiring harness than the 1975 truck. You'll need to either adapt the harness or wire everything from scratch.
* Computer Control (likely): 1985 engines were likely electronically controlled (fuel injection), while 1975 engines were likely carbureted. This means you'll need to deal with the computer, sensors, and wiring associated with fuel injection, potentially requiring a standalone engine management system.
* Exhaust System: The exhaust system will need to be modified or replaced to fit the new engine.
* Cooling System: The cooling system may require adjustments.
In short, while it's *possible* to put a 1985 Chevy engine into a 1975 Chevy truck, it's a major undertaking requiring significant mechanical skill, fabrication, and likely some custom parts. It's not a simple bolt-in swap. The feasibility greatly depends on the specific engines involved (e.g., small block vs. big block, specific engine codes).
