you can contact the supplier and cross your fingers they've got something in a suitable format!
I think I remember someone saying that iStockphoto.com has some vehicle vector art (though I can't vouch for the correctness)
here's a bunch of links I've collected, but I haven't been to them for eons so they may no longer be valid or whatever.
Good luck!
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Vehicle specs
http://www.vehiclegraphics.tv/veh_profile.php
http://www.vwrap.net/artspecs_ftp.htm
http://www.digitalauto.on.ca/
http://www.artstation-vehicletemplates.com/
You have to register for these sites, but the images are free for appropriate use:
http://gmassetcentral.com
Everything GMC/Chevy, plus Buick, Cadillac, Holden, HUMMER, Isuzu, Oldsmobile, OnStar, Opel, Optimum, Pontiac, Saab, Saturn, Vauxhall
http://fdaftoolbox.com All things Ford,
?http://lmdatoolbox.com Lincoln-Mercury (and maybe Jaguar?)
http://nissanartwork.com Nissan
http://hyundaiadplanner.com Hyundai
http://mazdamdrive.com Mazda (dealer rep. must give you access)
http://adplanner.toyota.com/ Toyota; must have dealer info as with some of the others.
http://www.kwikeesystems.com/ is good for product art