I'm in a similar boat, dropping a CBEA into a 08Ranger that had the 3.0. Essentially you need to keep the Ford ECU in the system to drive the cluster via CAN bus and retain mileage, etc, but can gut all the wiring for fuel injection, ignition, etc. My harness is stripped down to power inputs, CAN, ECT sensor, VSS, and the crankshaft position sensor. Oil pressure is a simple on/off switch, I haven't figured if it's normally open or closed yet, but it operates outside of the CAN bus, and you can always adapt the Ford sensor to the VW oil sender port. For the ECT/temp gauge, I'm installing a tee fitting in the coolant hose between the block and oil cooler with hose barbs and thread the sensor into it. Retaining the VSS will allow the speedometer/odometer to work. As far as tach, I plan to make a toothed wheel and spacer to mount to the front of the TDI crank with the appropriate number of teeth to mimic the original damper toothed wheel, and bracket to mount the sensor, it will require removal for serpentine belt replacement, but a small inconvenience to have factory functionality. I'm still trying to figure out something to operate the cruise control and retain the stock steering wheel buttons. Some of the LEDs in the cluster for warning lights such as CEL and fuel cap will need to be desoldered or covered, and hopefully a FF adapter can provide the VW CEL and glow plug indicator, which will require separate wiring to the cluster.
