I dont know im yet to download the Merc but if it helps this is how the standard one did it..
[item]
Arriva Transitional
repaint_body_g_3d
Arriva/Arriva Transitional.tga
[item]
Arriva Transitional
repaint_body_g_t_3d
Arriva/Arriva Transitional_Trailer.tga