I purchase the GCI paints from Rapco Parts. http://www.rapcoparts.com/manuals.html
The site is pretty easy to search. They give a short explanation of the era the paint color was used in. They sell the matching colors in both a spray gun form (can) and a matching rattle can form. They also offer the recommended primer and instructions to achieve the best results. (Xylene is an excellent reducer for this paint, and on the shelf at most Home Depots.)
Regardless of the vendor you choose, the GCI paints are very nice and will give you good results.