You'll likely need to address some aspects, possibly including:
* Motor Mounts: The motor mounts might not be identical and may require modification or replacement.
* Wiring Harness: The wiring harness from the El Camino may need modifications to match the Monte Carlo's system.
* Exhaust System: The exhaust system will probably need to be adapted or replaced to fit the Monte Carlo.
* Transmission: Ensure your transmission is compatible. If you're swapping the entire drivetrain, this is less of a concern.
* Accessory Drive: Power steering, alternator, and other accessories might require some adjustments to properly align.
In short: It's *feasible*, but not a simple bolt-in job. You should expect some fabrication and modification work. Experienced mechanics can usually handle this, but it's not a beginner project.