* Small Block V8s: These were the most popular choices. You might find a 305 cubic inch (5.0L), 350 cubic inch (5.7L), or even a 400 cubic inch (6.6L) V8. The specific horsepower and torque varied based on the year and any modifications.
* Inline-Six Cylinder: A smaller, more fuel-efficient option was the 250 cubic inch (4.1L) inline-six.
It's impossible to say definitively *which* engine was in *a specific* 1978 El Camino without more information, such as the vehicle identification number (VIN). The VIN will reveal the original engine.
When considering engine swaps (installing a different engine), the possibilities are much broader, but you'll need to consider factors like engine mounts, transmission compatibility, and exhaust system modifications.