I have made a digital dash board for a pre-OBDII nissan car with a consult port. I created the software that reads from the car and displays the dash however I want. The dash runs on a raspberry pi 3 and shows live speed, RPM, and coolant temp right now. Later I want to add check engine codes and the ability to clear them. The raspberry pi reads directly from the car's ecu through a USB -> serial port -> consult port adapter and then displays the data on a touchscreen that is mounted over my dash.
See it working here, and also how to do this yourself :) https://www.youtube.com/watch?v=5C9ypE6JUuY