That illustration doesn't appear in Kimble's book Cutaways
but he does explain his process in some detail.
Most of his renderings are 20 to 30 inches wide. They start as pencil drawings, often on multiple pieces of paper to separate the layers (vehicle exterior, chassis, engine, interior, etc).
Next, the drawings are combined and inked onto transparent film, much like a classical animation cell. Since 2005, Kimble has had his assistant Rick Terrell "ink" them digitally and then print them directly to the film.
Kimble then paints the back side of the film with Winsor & Newton designers' gouache loaded into an airbrush. He starts with the darkest colours and shading, then works towards the base colour for each part. He uses adhesive vinyl masking film called frisket, cut by hand, to mask off areas to be painted. Highlights and corrections are painted on the front side of the film, overtop of the printed line art.
The book is a great resource. It's as much a history of the American automotive industry as it is about his art and career.