The 1929 Ford blindback was actually made by Briggs in two different styles (60B and 60C). Try a Google serch on "1929 Briggs body wood" and you will come up with a lot of pictures of the body style. It may help you see how the bodies were built. It does show other body styles but should be of some help.
Here is site that shows a sedan undergoing restoration.
http://www.model-a-ford.com/proj_11.shtml
Gar Williams