Installation Instructions:
Drag and drop the contents of the 'models' folder into x64e.rpf\levels\gta5\vehicles.rpf
The 'files' folder contains a modified carvariations.ymt . This file is not strictly necessary,
and just allows the 'trailers' container chassis to spawn in multiple colors. 
Replace it in update\update.rpf\x64\data .

I also included the modified text for the carvariations.ymt file in a separate text document in the 'files' folder for anyone who already has a modified carvariations.ymt .

Enjoy!