This is a roadster design modeled using Delcam’s Power-shape software. This a hybrid modeller which means you can use solid and surfaces, and in the later versions Triangle meshes. I have produced many models using this software, it is easy to use but will take time to learn. Delcam offer a free to use version if you would like to try it. Visit Delcam.com
What I like about it is you can easily add a curve into a surface to change it shape and add surface together ( with the same no. of control rails). However I have now reached the limit of the software in producing a class A surface across a multi-patched surfaces. The need for class A surface arises if you wish to machine a large scale surface directly from the model as any small defects will show up in the machined part. Even so the software is still very good to develop a design.
This design was started with the full scale models of the men and the engine ( in this case a small block Chevy and Turbo 350 box. This give the scale for the car without allowing a design no one can fit in. Design modeled in 3d are much more build-able than artist sketch, but they do take much longer to produce.