This is what I see..
http://www.aquanuke.com/lorries.jpg
You may have to save the image locally to stop your browser resizing it.
I see your point about trucks, but in fairness they are kind of similiar.
But the top 2 are for lorries and you want folks to click on only the top 3 as there the highest earning adverts for you.. so it could work in your favour if the first three are highly relevant and the rest crap
Does what I see differ from what your getting ?