I just stumbled upon this site and it seems to have quite a few old car brochures and owner's manuals which may prove useful in identification purposes. It is not comprehensive for every make and model, but there is quite a bit there. I find some of these old manuals to be quite interesting and thought others might too. I also like their philosphy that all of this information should be freely available to everyone.

"The Old Car Manual Project"

http://www.tocmp.com/

http://www.oldcarbrochures.com/