> If you delete the faces, the sides of the truck are transparent from the inside.
You have to add faces to the inside to prevent that.
> I'm not going to release it
Then why tell us.
> unless Slickster says I can (Because of some arguments).
The biggest argument is releasing things without significant changes (or without permission or without credit). If you take a closed in truck and open it up, and credit the original model, nobody is going to complain.