Finally done. Done in DHD,HD,SD sizes.
Haven't tested ingame so any feedbacks are welcome.
This is all I could accomplish despite the skinning restrictions.
Don't forget to backup all your files before installing!
Installation guide : Just click on the size you want for your car, either DHD,HD or SD. And copy paste both the cars folder and the raceload.jpk into the game's main folder.
Hope you guys like it.