First take the blueprints, crop them in Photoshop and place them on planes (for a tutorial see: here)
Now start drawing splines along the edges of the car in the front view (or side, just the view where you see the side of the car). I assume you know how to draw splines and how use the sub-object qua vertices (bezier, bezier corner, smooth and corner). If not then look in the Help file that ships with Max. Make sure that you always form triangles or preferably squares, never make a 'face' with five vertices, because it will not work then (the surface modifier that is).
Next is placing all the vertices of your spline at the right place in the last and third dimension. Do that by using the top view: align all the vertices at the right spot. From here on it is pretty straight forward: do this for all the different parts (front / rear bumper, roof, hood etc.) Make use of the great tool called snap (see Help file for more info). When you did that, add a surface modifier to your spline(s) and you have a perfect mesh, try to play around with the segments number and see what happens. An extra meshsmooth always helps too for a final touch.
The rest of the images is the progress of the scene I used (my favorite car: The Lancia Delta Integrale Evoluzione).
And here the final result: