* Engine Control Module (ECM): The computer that runs the engine is vastly different between those model years. The 1999 system won't be compatible with the 1995.
* Wiring Harnesses: The wiring harness connections will differ.
* Sensors: Sensors and their locations may have changed.
* Emissions Systems: Emissions regulations tightened significantly between 1995 and 1999. The 1995 system might not meet 1999 emissions standards.
You might find some overlap in the *type* of engine (e.g., both might be 5.7L Vortecs), but the internal components and associated systems would require extensive modification or replacement to even attempt a swap. It would be a very difficult and likely impractical project.
To find compatible engines:
Focus on engines from 1999-2000 Suburbans. Engines from these years will have the best chance of being directly compatible. Even then, you should verify the engine code on your existing engine and the potential replacement to ensure compatibility. The engine code is usually stamped on the engine block itself.
Swapping engines is a major undertaking. Consult a mechanic specializing in your vehicle's year and model before attempting this type of repair. It's often far more cost-effective to rebuild or replace your current engine rather than trying to source and install a different year's engine.
