Now, lets start modelling that car..

When modelling such a complex form such as a car body, it is very important to have some good references...

There are several places on the net where one can find blueprints, good places to start are here:

http://www.suurland.com
http://www.onnovanbraam.com/

I would also try to find as many good reference photos to use as a supplement to the blueprints.

For my Pennzsoil Nismo I started with these blueprints:

After retrieving some good blueprints, you need to place and align them in your top, side and front viewportst.: