Glen, before you start making the knobs you might want to research a bit more so you make the correct knobs for people's needs and desires. The A's, B's and C's used the same knobs, only the color was different. Some speedsters had a very small knob, same shape, on the extreme left for the wiper switch. Mine operates the fog light switch.
Let me quote/copy from "A RESTORER'S GUIDE TO AUTHENTICITY" by Dr.B. Johnson, page 96. "Most 1954 - 1959 356 and 356As had these combinations: ... The knobs always matched the steering wheel color (wood not included)and always matched the window crank knobs, escutcheons, and shift knob. There was also a correlation between top frame color and knob color in Speedsters; the early cars tended to have black frames, and no ivory frames were made. (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is) frames generally went with (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is) knobs, and tan frames with beige and ivory knobs. Frames on later cars were tan only. In 1960, or very late 1959 by some accounts, all plastic components went black.
The knobs on my car are correct for the speedster, by the way, a 1959 356 would be an A car not a B. B series was started in 1960.
Most 1954 - 1959 356 and 356As used knobs that were color keyed to upholstery color, Red uphols=Beige knobs, Brown/Tan uphols=Ivory knobs, and Black/(leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is) uphols=(leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is), (leave as is) knobs.
All this is much more than most of us need or want to know. Sorry, I'm bored tonight.