The Shelby American World Registry would be the most complete reference available. It costs $125 and is available from http://www.saac.com and Tony Branda and other Mustang parts vendors. This book is a must for any serious Shelby Mustang or Cobra shopper.
The Registry is by far the best source. It even has illustrations for the stripe dimensions and lots of other great info. Also, stop by Barnes & Noble or one of the major book stores and check out Muscle Car History Shelby Mustang written by Tom Corcoran a long time Mustang writer and previous Editor at Mustang Monthly. It's published by Motorbooks International. You may want also check with the many companies that sell classic auto literature and pick up an original sales brochure. I see them on E-bay all the time. Also, Tony Branda is selling 1965-66 Shelby Mustang GT 350 Press Release Kit Portfolios. The 65 kit is $59.95 and the 66 kit is $39.95.