* 5.0L (305 cubic inch) Small-Block V8: This was a very popular choice.
* 5.7L (350 cubic inch) Small-Block V8: Another frequently found engine.
* 6.2L (377 cubic inch) Diesel V8: A less common, but available, option.
To know for sure which engine is in *a specific* 1991 Chevy C1500, you'd need to check the vehicle's identification number (VIN) or look at the engine itself for the displacement markings.