* 4.0L Cologne V6: This was a common engine option.
* 4.6L Modular V8: This was available in several variations, depending on the specific model (GT, etc.). There were differences in horsepower and torque between these versions.
To know the exact engine in a specific 2004 Mustang, you'd need to check the vehicle's documentation (like the owner's manual or the vehicle identification number (VIN) decoding).