Hey rod, I don't know that you have many other options besidea mcfarlane.
I would suggest that if they are just stiff, lube them. I've done this two ways, the first is to spray some lube(i like lps 2 or tri-flo) in the end of the cable then use and air nozzle to force the lube up the cable. Repeat this process several times to get the cable lubed throughout the entire length. The second method I've used is to remove the cable from the airplane and soak it in a tub of 5606 hydraulic fluid overnight.
The cables in my '56 are very simple(guessing they are the same as yours), just a steel wire in a steel sleeve, so there isn't much to wear out, however they do get dry. My cabin air and cabin heat cables tend to hang un and get stiff, but that is usually the flapper/slide mechanisms that need lube, not the cable.
Good luck, you got my number if you need help or have questions.