Before we completly get off the subject, your comment about the 3 way switch got me thinking (ok so that can be scary ).

The 60 to 61 (?) Chryslers had a dash mounted turn signal switch (it was held with an elecromagnet until a small cam lower on the column broke the circuit).

My wifes 90 Le Baron convertable also had a dash mounted turnsignal switch (don't know how complicated that wiring is). I would think either either should be able to be adaptable to a a rod dash without too much work.

I'm just throwing that out there as food for thought in case someone can use it for their project.