If you noticed my post above...I commented on how the "Overflow tanks" are not original.
The color of the M/C cap would depend on the supplier of the Master Cylinder. Ford used a few different suppliers. I can think of a few, Kelsey Hayes, Bendix, Lockheed, and even possibly Wagner, but can't confirm that last one 100%. Master cylinders were subcontracted out to other suppliers. I would say that Zinc or Black are acceptable, and they should be made of metal, not plastic! lol.
What the pictures give you is an excellent idea of how your engine should look. These are original cars, unrestored. Notice the lack of chrome....other than the aircleaner.
That is how they all came.
Other chrome "goodies" were available over the counter and added later by previous owners on most of the cars you see today. (Lots of restored cars)
Take a good look, The pictures are a great glimpse into the past.
Tony K.