To be absolutely certain:
1. Consult your owner's manual: This is the most reliable source. It will show the firing order and a diagram of the distributor cap.
2. Look for markings on the distributor cap itself: Some distributor caps have the firing order printed on them.
3. Use a reliable online resource: Search for "1991 Camaro RS V8 firing order" and cross-reference it with images of distributor caps.
Relying solely on general information can lead to misfiring and engine damage. Always verify with your car's specific documentation.