That's actually just a game bug, if you take a mod out after making a custom config and have custom configs on, for some reason it will still show up in the vehicle selector. However, if you try to spawn it, it will spawn nothing.
I remember Urbanmaid saying that it won't be released on the repository because the file size is too big to put it on there
He's probably using geforce experience or sometihng like that, if that's the case he can't access the files of the computer he's using beamng on.
That's the only way I got mods (Drops mods folder into repo) Only American Fullsize series by SergentFido was downloaded without this
btw it's not really important but you should put them in the mod folder itself, it's not gonna break anything but it's how you're meant to do it.