Your point is to install all cars in gta3.img at once? Try to use Crazy IMG Editor.
Click here : http://www.gamemoddi...img-editor.html
EDIT : I found a better link.
Okey i know i can search for a cars name in the gta3.img to replace it, But that does not make it any easyer. Still te same procedure as with SAMI, Do you know what file i have to search for and how to replace it so i can move them all at once?