I didn't see any issues with it. I think it must be something to do with your file names. --- Post updated --- It was so obvious. How did I not see that. He's right.
And here is the whole vehicle file (don't leak) --- Post updated --- lol thx --- Post updated --- Wait a sec.
You didn't put a "vehicles" folder in you zip file before foxbody and in the material it has vehicles/foxbody.
Well yes but idk how to fix this car --- Post updated --- It's the barstow. --- Post updated --- I have put it I didn't want to share the rest of the car pack
If you don't want to share your whole file, you can use the private mod support in https://wiki.beamng.com/Mod_Support go to the last line then click at "create conversion".