Here's a nyc taxi skin I made for the grand marshall. Things to note: the logo's are reversed on the passenger side (no way to fix this) and the logo's have a goldish tint to them.
Theoretically you could reskin the police decals to be taxi decals without editing the mesh and get unmirrored text on both sides
Which file is used to show the police decals? I looked at the fullsize_police.dds file, but it's just blank white on my end. I've tried opening it in photoshop, paint.net, and GIMP. Nothing shows up, just a blank image
It's in vehicles\common, called decals_police.dds. You won't be able to make it completely separate without editing the mesh (it's assigned to the material decals_police) but you could overwrite it with taxi decals.
Right click on the beamng drive icon and select "open file location". Then go to vehicles, fullsize, and paste it in the fullsize folder. Make sure you make a backup of the original encase you want to revert to the original color.
Did you put the files INSIDE the "nyc taxi" folder in the <beamng directory>\vehicles\fullsize folder? Or did you put the "nyc taxi" folder directly in the vehicles\fullsize folder?