* Engine Bay Size: The Neon's engine bay is significantly smaller than what's needed to accommodate the larger Subaru WRX engine. You'd likely need extensive modifications, possibly requiring custom fabrication of mounts, firewall modifications, and potentially even bodywork alterations.
* Transmission Compatibility: The WRX transmission won't bolt directly to the Neon's existing drivetrain. You'd need a custom adapter or a complete drivetrain swap, including axles, differential, and driveshafts.
* Wiring Harness and Electronics: The WRX engine's computer and wiring harness are completely different from the Neon's. Integrating them would be a massively complex undertaking, requiring extensive custom wiring and potentially a standalone engine management system.
* Cooling System: The WRX engine has different cooling requirements, meaning the Neon's radiator and cooling system would likely be inadequate.
* Exhaust System: A completely new exhaust system would be needed.
* Cost and Complexity: The project would be incredibly expensive and time-consuming, likely exceeding the value of the resulting vehicle. It's a major undertaking that requires significant fabrication, welding, and electrical expertise.
While technically *possible* with an extremely high level of engineering skill and a substantial budget, it's not practical for a typical home mechanic. The effort and cost would far outweigh the benefits.
