Let's make a StepVan: Step 7: merge the shapes

Here's where the real work begins. There are three operations you need to learn: Union, Intersection and Subtraction.  I'm not going to go into those here at this point, but I am going to use the terms.

The Red part below has slight curve along the upper edges. We'd like to impose curve that on the Green part. This van is 8 feet wide, 23 feet long, and 9 feet high.  You need to keep those dimensions in mind as you work thru this part of the model.

Take the Red part and stretch it to 25 feet long, making sure that it stays centered around (0,0,0).  Then, take the Green part and make it 8 feet wide, also centered at (0,0,0).

Then,  using the Intersection function.. intersect the two parts. You should be left with the overall shape of the final body. The front slopes should be visible, as well as the curves along the upper edges.

Note: doing this takes time and patience, trial and error.  You have to learn the quirks of TrueSpace, and sometimes it can be frustrating.  Don't give up.. keep trying.

Now, take the Door shape, and copy it so you have two of them. Position one on each side such that they overlap the main body by 0.25 units (3 inches real world). They should stick out from the side some, but only extend into the body by 0.25.

Select the main body, and then subtract the doors from it.  This should give you the main body with the doors recessed into it.

Repeat this step for all the smaller pieces. You are effectively "whittling away" at the main body, using the various shapes as knives to cut out the shape you wish.

Piece of advice: Save, and Save often. Way too many times have I spent hours cutting and shaping, only to have the program die on me, or to make a cut incorrectly, losing several hours of work.