I based this model on the CAT 769 dump truck. It's not super accurate by any stretch, and in fact I eyeballed the whole thing instead of actually measuring anything. The total build so far is just over 12 hours over the last several days.
Now I didn't build this exactly in this order, but it shows the layout of the model:
Engine block. Not at all accurate, as it'll be hidden in the model most of the time but it is visible dimly from the side at points, and has to just look mechanical enough to fool the average movie watcher.
Wheels. The wheels on this truck are as tall as a person, so I had to load in a character model as reference to base the rest of the model on.
Adding the cab. The best thing here is I can build other stuff on the back if I want to change the truck. (Which I will need to do :)
And the dumper, ready to cart away the mountains of cash that will be coming my way soon.
All that's left is to 'dirty' up the model with some procedural noise and some vertex colors, and to apply my 'polygon paint' effect to the whole model.
Update with the texturing and paint method applied to the model: