Beyond The Exterior
Rear Cab Wall
This wall is just a single surface of polygons set up to create a barrier between the cab interior and the trunk area. Of course, It's nice to do it in such a way that we get the ledge underneath the rear windshield. If we copy the points along the rear edge of the cab opening in the rear car section, we can paste these points into the structure manager of a new polygon object with HyperNURBS applied. Paste the same points again and set the new points to the same Z value at about the depth you'd like the ledge. Use the bridge tool to create the polygons between these points.
Next, you can create the forward facing panel of the wall by pasting copies of the edge of the ledge, then dropping them down towards the chassis.
After all that, use some knifecuts to sharpen edges, particularly the bottom of the wall, and up top near the edge of the shelf. I also did a fairly soft extrude inner followed by an extrude on my shelf polygons just to add a bit more character.