when I replaced the heater core I had issues with two heater control cables. The defrost cable I re-routed so it actually functions as it should with no binding; the knob NOW faces DOWN, with minimal bends in the cable.
With regard to the heat control valve I completely did away with the cable and instead place a vacuum operated heat control valve that is either open or closed. You want heat, you get heat; if you do not then you will not have it, simple. I used a pull knob switch in place of the cable knob. The new knob operates a electrically operated vacuum switch that allows vacuum to open the heat controlled valve. Sounds complicated but in reality it is simple. I have owned a EB for the last 48 years and my heater/defroster system has NEVER worked this well before. Just another way to skin a cat so to speak. There are alternatives to some of the age old EB engineering shortcoming, in my opinion. Now, if I could just come up with a better small block thermostat housing setup, I could make a fortune!