The Star Swordsman - Yep – that’s exactly what I’m going to do one of these days: Skim through the film frame-by-frame in an attempt to nail down that stinkin’ truck. (snigger)
Cars_Nemo_Fan - Haha – that’s pretty funny, actually! Thanks for the laugh. 
If the truck stank, we would have tracked it down already! 
My guess is that it’s in there. Just small enough that the resoloution on the DVD makes it look like any old truck. Heck, maybe when the Blu-Ray comes out, we’ll be able to find it! 
Here is another reference that may be to Cars (specifically Mater) in The Incredibles:
The part where Syndrome says “This is tooooo good!” in a hick voice, like Mater. This could be just a coincidence, though.
I think that has been done by me and many other members of this board before Mitch.