[Early_S_Man]

Do you have a Bentley manual???

Speed and reference sensors are identical, so one spare can be used for either application.

What makes you think you need one? I know many on this board recommend replacement based on symptoms alone, but if you haven't looked at [tested] the signal with an oscilloscope while cranking ... you can't be really sure! There is a clearance adjustment that is quite critical ... and should be done or verified before declaring the sensor bad.