Did you ever find out how to do this? I tested one just to see and put it in the newest patchday (used a file name polterminus to replace the Canis Terminus) and it did not change. Went to the patch day it was in and replaced it and while the model did change in game, there was a million liveries that obviously didnt match and looked horrible so ended up deleting it. Just curious if anyone has had luck replacing those vehicles, would rather replace them all to new models so NPCs arent driving around vanilla cars LOL!

polterminus sounds like it’s one of the newer cars somewhat recently added. Their liveries work different, called modkits now I think?

yea its one of the new cars. I dont like the generic cars and wanted to change up the new ones. But they have a million liveries and i can delete them but the vehicle i try to replace with will load in just black with no livery. So wasn't sure if we can replace them fully or not