Scale it down with the cusor on the 0,0,0 point of the car, in edit mode, s-key, and scale to desired size. Blender has "edge length" button.
Rotate car by selecting all vertices in edit mode and rotate so front of car is to the left, top up, 90 degrees.
Select both sides and join with j-key, name the object body. Make sure all vertices are selected in edit mode, and remove doubles.