To be able to change your HUD between the two settings if you live near the border or plan on taking a trip to the other country.
On the HUD display in the dash, the ground wire from Pin 7 runs out of the HUD to C200 pin J4 (the single connection point for all dash wiring). From there the MPH cars don't have a wire coming out the other side of C200 and then going to C332 pin F (RH ground buss by passenger feet).
For MPH, no ground
For KM/H, grounded.
Add a switch to ground and to pin 7 or the right cavity on C200 and you can choose between KM/H or MPH.
Keeping safety first and abiding the laws...one mod at a time.