There used to be something called Dart Fonts which fixed the number plates, destination screen and missing engine cover door.
But I think that got lost with Aussiex. They also had the latest version of the Dart which had all three of those things included.
I searched up "Dart fonts OMSI" online and a link took me to Man1333's Garage Facebook page.
From here there were links for three resources - the Dart vehicle Beta, something called trial repaints and the Dart Fonts
I haven't tested these links - they are from 2012 but still worth a try.