* Small-block V8s: These were the most prevalent. Sizes included the 5.0L (305 cubic inch) and 5.7L (350 cubic inch).
* Inline-6: A 4.3L (260 cubic inch) inline-six-cylinder engine was also available.
To know the exact engine in a *specific* 1990 Silverado, you'd need to check the vehicle's documentation (like the owner's manual or the vehicle identification number (VIN) decoding).