* Engine Differences: Even within the same model, engine types, sizes, and computer systems changed over those four years. The 1995 and 1999 Malibu likely used different engines (different displacement, potentially different configurations like V6 vs. 4-cylinder). The engine control module (ECM) and wiring harness are almost certainly different and incompatible.
* Computer System: The 1999 model likely has a more sophisticated computer system for emissions and performance control. The older engine's computer would not be able to communicate properly with the newer car's systems.
* Mounting Points: While there might be some similarities, it's unlikely that the engine mounts will line up perfectly. Significant fabrication or modification might be needed to physically install the engine.
* Transmission: Compatibility between the transmission and engine is crucial. Even if the engine fits, the 1995 transmission might not be compatible with the 1999's drivetrain components.
* Emissions: Older engines may not meet the emission standards of the 1999 model year, leading to potential legal issues.
In short, while some parts *might* be interchangeable, a complete engine swap is a complex undertaking that would require extensive mechanical knowledge and potentially considerable fabrication and customization. Finding a used engine of the correct year and model for the 1999 Malibu would be the much simpler and more reliable solution.
