Gene,
They are kind of special, just think about this...
They came out in May of 31 and were only produced for about 7 months.
For Ford to do something like that it had to produce a benefit. It was the first all steel structure fordor for Ford and it was produced with all interchangable parts between Ford, Murray and Briggs (though I was never sure if Ford ever built the body).
Wood was only used for the top and for mounting interior parts.
The labor savings and body cost must have been phenominal for Ford to make the change. The build up costs of the earlier fordors must have been significant. Plus it required more expensive skilled labor to build the wood frame and then nail the metal to it.
It was also the first step towards better styling. I would guess his son had a say in the design. But the slanted windshield may have also been a safety feature. The parallel glass of the straight window bodies were a hazard at night. Parallax (the reflections between the front and rear windows) made it difficult to be sure if a car was coming in front or behind you.
The body also incorporated the new seating postions allowing for a bit more seating room.
I do not know if that helps, but the body style is very pretty. I really wish I had bought a very original and nice car that was avaialable back in 2000 instead of starting down the road of the cabriolet. With my young boys a fordor would be nice.