- On or around Feb 2008 Ford changed designs of the spark plug. They are a completely different thread than used from 2005 until the transition sometime in 2008. If your 2008 Mustang was built in 2008 you should consult with us before you purchase. You can identify which plugs you have by looking at the boot color of the coil pack. Black boots are used in 2005 to mid 2008 which is NOT what these plugs are designed for. Brown boots are mid 2008 and newer which are these spark plugs.