Where is the number six spark plug on a 2003 3.8 Ford Mustang?

The firing order for a 2003 3.8L Ford Mustang is 1-3-7-2-6-5-4-8. Therefore, the number six spark plug is located on the passenger side of the engine, towards the rear. It's helpful to use a spark plug chart that shows the location of each cylinder for your specific engine. You'll find the plug near the back of the engine's valley, somewhat hidden. Always consult a repair manual or diagram for your exact year and model for the most accurate location.