Bob,
Consider the Town Car production from the point of view of Briggs. Ford's order was small (based on Brigg's capacity) and production was done in batches over four months. Fastest & easiest method would be to paint all the bodies black. Notice that on painted bodies that the interior door jams, interior & exterior cowl, and upper body remained black.
Examine a Briggs built Bronson Yellow Cabriolet. It actually starts as a Seal Brown body inside & out, later having the sides painted yellow. Making a profit from Ford required streamlining production methods.
The January 1929 Service Bulletin is significant as it describes the paint color layout. Some time in the late 1970's a Town Car was painted with the top of the gas tank & hood black to appease the owner's taste but is not Ford / Briggs correct.
Briggs production records are long lost, the paint considerations are from Tim Kelly's research.