I now have my heating system all up and running. And, I DO understand your frustration. Omix sells cables that are a bit too short and I could not find a new replacement for the one you mentioned. On my 1990, that cable has an "adjuster" built into it that changes the effective length, used for rigging. That "adjuster" is part of the cable and is located just beyond the control panel (between the control panel and the firewall). I believe some model years did not have that "twist action" adjuster, but mine did. I spent weeks on ebay, buying cables that I "hoped" would work. 90% of the ebay listings misidentified the cable they were selling. I even resorted to buying cable "sets" that were advertised to be the three main cables, but when I received them, two of the three were identical and none were the fresh air vent controls. I even found that the color coded plastic hold-down brackets were inconsistent. I now have many extra heater control cables laying around!
I ended up looking for a replacement upper ventalation duct that fits directly beneath the cold air intake at the base of the windshield. I found one on ebay that still had the cables attached to it. (Remember, the fresh air vents have two separate cables that work in series across this duct). I studied the heck out of the photos to insure that the color-coded hold-down brackets were not broken (many were) and ended up with the entire upper duct assembly, including the desired cables, but also the vacuum motor and fan speed resistor pack. I took the cables I needed off of this duct and used them to get my fresh air system working properly. It was a pain, and I still have that purchased duct sitting unused in the garage.
Another note... I used a new Omix replacement cable for the defroster air door control, even though it was about 3.5 inches too short. To make up this distance, I re-routed a more direct path to the door control rod (abandoning the firewall tie-down point), then reworked the clip that binds the cable to the control rod such that only one of the two cable grab-barbs were holding the cable (Hard to explain). The symptom when this cable is rigged too "short" is that you can't ever move the defrost lever on the dash to the "OFF" position, leaving the blower motor running 100% of the time whenever the ignition is "on". That defroster cable length is critical.
Working under the dash on these cables was one of the worst jobs I ever took on with the Jeep. I had to remove the air conditioning duct work and blower motor, and opted to remove the drivers seat so I could lay on my back with my head hitting the brake pedal. I never seemed to have enough light. I also removed the engine instrument cluster, radio and speedometer to gain some access holes that my hands could fit through. Even then a lot of the cable work was done more by "feel" than by eyesight.
Lastly, and this should hopefully not affect you, after I had everything back together, rigged, and running perfectly, my heater core started leaking. That adventure is another story, just suffice it to say that the defroster control cable had to be re-rigged after heater core replacement. I can understand why many YJ owners simply remove and bridge the heater hoses (sacrificing any cabin heat) instead of tearing into that lower duct box to replace the heater core!
