Fast forward to solving my issues thanks to some great earlier posts with photos on this forum. So - I got the 2 OMIX cables and installed them. The “red” cable they offer is for the rightmost of the two sliders viewed from the top of the control box when you slide it out. The “blue” cable is for the temperature slider and the eyelet simply goes over a hook in that control lever when viewed underneath the control box. The third cable is the one that they do not offer a replacement for, so reuse yours with care. I did the same thing that the OP did to secure it to my control box using a zip tie after drilling a small hole next to the mounting pedestal. You can use the plastic barrel assembly to adjust it in or out as you line up the eyelet to snap over the stud on its slider. I also used a pliers to run the eyelet in and out a few times before doing this just to be sure that I had full travel at the other end on my HVAC box. For the “red” cable - the replacement was inches shorter than what I removed from the Jeep. The original was secured to the firewall with a screw and grommet. You won’t be able to secure it back that way but no big deal. I left the other end of the “red” cable loose on the air box and only slide it onto its post after reinstalling my control box back in the dash. I also used a zip tie to keep that cable from rotating around in its post - had to make sure that it stays aligned after putting the control box back in place. By the way, my control box had much of the mounting post material broken away and gone, so I got a good used one on eBay before tackling this job.
For my chronic valve cover leak - I learned that the old plastic 4-cyl valve covers are known to do this, so I installed the later, aluminum, valve cover (bought from an eBay seller who also included the 11 bolt/studs and the heater hose/electrical harness retainer) from the 1991 and newer 2.5 4-cylinder per a different post on this forum. Be sure to also buy the gasket for a 1991 Jeep as it’s different from the one that went with the plastic 1990 valve cover.
Like the OP, I used zip ties to secure and align the control cables. The “red” cable is the bottom of the two seen in the OP’s photos which I marked up in blue to show where I used zip ties.
Here’s the “red” cable that OMIX sells. The red side clips in on the air box and you slide that metal piece over a stud on the air door lever itself. You can unhook one side of that to adjust the position of the metal piece along the bare cable itself in order to ensure that you get full travel of the air door lever.
Here’s where the OMIX “blue” (temperature) cable is attached - farther to the right, under the glove box. For this cable, the blue fitting snaps onto the lower side of your control box. When you move the lower slider you are extending or withdrawing this cable and thereby making that lever move left or right.
