yes , that is what I thought. Servo Bypass means HIGH COLD and HIGH HOT!
I downloaded the factory 123 manual from the website. It has details of everything.
http://skinnerbox.steaky.org/Service/W123/Index/110index.html
Here is what I think maybe could be configured.
Bypass the servo in the familiar format and use a cable. The vacuum lines could be simplified into 1 or 2 lines such that all vents come (or just Bi-level mode) on when any button (or just bi-level) is depressed other than OFF. It seems the only use of the vacuum lines are to actuate the different air vent valves to redirect the air from center vents to lateral vents to floor, etc.
This would simplify fixing all of those vacuum lines which looked cracked and old on the servo side and simplify trouble shooting the vaccum system. There are prob. a few tubes that are good, so I could use them. This can be done under the glove box, or at the servo, by just using barrel tube connectors.
The next problem is how to get the blower to run at different speeds. I found the blower under the glove box. I can access the power wires and use a power supply to see what voltages give what speeds. I can then maybe use the potetiometer of the temp wheel to vary a voltage straight from the battery to vary the blower speed.
So temp control comes from cable, vent control is simplified, and fan can be turned down by the wheel.
Sounds crazy but i think it can be done.