There is a mod that I created called "Truck Fixes". It contains various fixes for several modded trucks including the GTM T-800, GTM 567, and GTM W900B. On the GTM trucks, it fixes the mirrors, headlights, reflection issues on the interior glass, the bad audio reverberation in the interior, and adds support for the interior shadows. I also created a mod called "Real Good Headlights for Modded Trucks" that provides even better headlights for the GTM trucks and others.

There is more info available on the Truck Fixes mod in the discussion area of the Real Good Headlights mod here on Steam. Go here:

https://gtm.steamproxy.vip/workshop/filedetails/discussion/3413941328/598522845445770951/

-Maurice