I found this tutorial about how to use a raspberry pi to add a digital panel to old cars (canbus port needed)
That’s deeply unwise. Nothing you cobble together yourself using a raspberry pi is going to be up to automotive safety standards.
Anyone who sets up one of these has nobody but themselves to blame when it misbehaves and gives them incorrect information, or no information, or starts flickering distractingly, and they get done for speeding/hit a pedestrian/fail whatever inspections the law requires in their part of the world
I think you may be overestimating how far safety standards have come in a very short amount of time. I’ve driven cars from the 1960s up to modern day and anything before the mid 90s would be fare less accurate and reliable than I could cobble together on a RaspberryPI.