Well, time to let the cat, er, crackerbox out of the bag. I had cut a couple of the cab parts from sheet styrene and was surfing for more reference material when I stumbled on the fact that Shapeways had a 1/14 Crackerbox cab available. In fact, they offer 4 styles! Big sleeper, single sleeper (my real favorite), no sleeper w/solid back wall and no sleeper with back window. I couldn't resist ordering one and it came today. All I can say is WOW! This is my first experience with 3D printing and I'm quite impressed with the level of detail. Panel lines, door seams and handles, even the handles on the nose to tilt the cab with. Here is the cab straight out of the box and mocked up on the chassis.
It's going to require moving the axle forward slightly to get cab and chassis to line up but other than that it scales out nicely.
I was very impressed with Shapeways customer service and their commitment to customer satisfaction. SLS plastic can suffer discoloration from oxidation during cooling due to the size of a truck cab. I was contacted prior to shipment, sent almost a dozen detailed photos of the discoloration and asked if I was happy with this cab or wanted another one built. As paint will cover the slight yellowing and the oxidation will not bleed I accepted the cab. In person I really can't detect any yellowing, but their concern was refreshing in this day and age.
All in all I am very happy with my decision to go 3D printed, and I can always do the single sleeper version with the parts I have cut. Now to move the axle, fabricate a floor and hinge the body.