Factory / dealer Columbia differences & '37-38 heater Qs

[CBoz]

In an earlier post, George Trickett pointed out that 37 - Feb. 39 factory Columbias used the single long speedo cable, while dealer and aftermarket installations had the speedo adaptor setup. Why the difference? Just from looking at it, I would think the long speedo cable would be problematic.

Also, my understanding is that up to a certain date, '37 Zephyrs had a center-exit right side exhaust manifold, requiring a heater setup that looked something like the one pictured at the bottom of this page:

http://home.mindspring.com/~bozarth/id4.html

Does anyone know when the '37s changed over to the front-exit exhaust manifold, requiring the change to a heater system that looked like this:

http://home.mindspring.com/~bozarth/id6.html

My car had a scheduled build date of 3/1/37, and I'm trying to determine which was exactly correct.