I put a lot of mods now when I see the car starts not appear unless 4 of them
Google "Carstockalypse", download it and put it in the C2 root folder (along CARMA2_HW.EXE).
Download C2 addon cars from the internet, extract the content of zip/rar also in the C2 root folder.
Run Carstockalypse.exe and if you did the above properly you should have available cars to install.
Always read the readme text files that come with the addon car archives as sometimes, additional steps are required (adding a sound to SOUND.TXT).