I thought I would share this one...
http://www.flickr.com/photos/vossenwheels/page1/
There are heeps of unreal donors on Flicker, and when you are lucky, they are huge hi res formats! You just need to know what to search for....
http://www.flickr.com/photos/theperfectexposure/sets/
....This is another cool set of images ,All hi-res, All big sizes, lots of cool cars.
I hope this helps, if not for donors/bases, but for inspiration. There are a heap of cool cars to look at. I spent the whole bloody day!