Ah, there is the problem, don't install in x64e. x64e stopped working a few updates ago I think, and all the install locations have switched up a bit. For all vehicles, put them in patchday9ng. If you follow the same folders, there is a vehicles.rpf in there, in which you can put all of the vehicle mods you have, even if the readmes say to put the somewhere else. But you still have to put the carvariations.meta, etc. into where the readmes say.
When the game updates again, check to see if ur cars still work, if not, then hold off until the mods get up to date and they say in the readmes what the new installation directory is.
...If that makes any sense :)