here is an enclosed trailer it works with trucks with a hitch it was converted to sp and you can change the colors and wheels and open the doors there are extras with the trailer the trailer can fit 2 cars depends on the size of the cars. 

to install put the file in dlcpacks and openiv 

<item>dlcpacks:/dltenc/</item> 

spawn name DLTENC in utility category 
to add the trailer to a car go to vehicles meta put 


  <Item>dltenc</Item>

under trailers in vehicles meta