will hooking up the harnesses from the D3 to my Ford harness be enough to get the VSS to work seeing how it already has a speed sensitive volume or do I need to hook up the VSS wire from the D3 harness to the Ford harness

if there is a grey black wire in your radio harness, use it. if not use this

Speed Sense gray/black ac ABS or brake system control module

The ABS control module is on the rear driver side of the engine compartment. On the Hybrid models, the brake system control module is on the rear passenger side of the engine compartment.

On vehicles with the 6-disc in-dash CD changer, this wire is also found in the radio harness.