There is only 1 input to the speedo from the skid control ecu
There is only 1 out which splits into 3.
I would tap into connector C12 PIN 18 (gray wire) on the back side of the combination meter.
This is the INPUT from the skid control ecu and the speed sensors. This signal is digital (I THINK).
As it passes thru the speedo (combination meter) it is converted to ANALOG and then goes out to the factory NAV/Multi display and the HV ECU.
It maybe analog in and digital out. I am not sure.
You could also try that wire Connector C11 pin #6 (white wire) on the back of the combination meter as well.
TIS is on a new program so I cant post pictures as of yet.
E-mail me and I will send them to you. The picture of the connectors and loctions.
mustang67408@cox.net
Hope this helps