Well if you can make up all the parts needed as you've done with the brakes, you shouldn't have any problem with the Cyclo cable.
It is one cable with a shifter nib soldered to the middle of the length. Sheathing on either side of that nib and then the other end(s) are soldered together to another nib The nibs fit into recess' in the shifter barrel groove on one end, and the the barrel wheel that is on the derailleur shaft. It creates a push/pull movement. All the derailleur movement comes from inside the derailleur arm mount where there is a helical roller channel that slides the arm back and forth across the shaft as the cable is pulled about 60 degrees either way.
My version uses the shifter tension as the only means to fix the derailleur placement. The next version had a flat helical coil spring along the derailleur shaft that helped keep tension in one direction and the shifter held that spring tension.
My set-up is curious to me in that the shifter had no means of tightening or adjusting the tension at all. Other similar shifter versions Ive seen have a tightening screw in the center but mine was a brass rivet. When I re-did the shifter, I replaced the rivet with a brass post that works to adjust tension. I did have to make a bushing to make the post work, but it now looks and works like it was made that way.
Notice the stamping on the derailleur arm, that number at top is the year of manufacture.
If you haven't settled on a year of manufacture, yours could date your machine.
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