Uh, some confusion arising here. First thing to confirm is that what you have is a 350, aka TH350. Reason for this question is that 350's only come with a kickdown cable for passing purposes. Otherwise all the shifting gets taken care of by a vacuum line to the modulator valve located by the tail shaft housing on the passenger side of the case. Even the "E" variant that has the lockup converter still is govermed by vacuum.
It is only when you get into dealing with the 700R4 and the 200R4 units that you start to find the shifts being governed by a TV Cable that connects to the carb at the engine and to t-mission down on the passenger side. This TV Cable is connected to a wire link internally in the t -m.
In order of appearance, the throttle cable is anchored in a bracket located beside the Timer. That bracket has two square holes in it and the upper is for the carb throttle cable and the lower is for the TV cable. Be aware that there are multiple versions of that bracket and that they land closer or farther from the carb according to what their OEM was.
The throttle cable housing just snaps into the bracket. Once it is set you pull the cable out and attach it to the pivot point on the carb thrrotle lever. Done. You may still have to set the idle stop but short of swapping in a different mounting bracket there is no way to "tension" the throttle cable and no reason to; it sets itself.
The TV cable is a whole NUTHER kettle of worms. It has to be tensioned correctly. Too little tension and you get late shifts; too tight and they come too soon. Either situation if left unremedied will result in the death of your slush box.
The steps for this are almost worth surfing U-tube and finding a video or scoring a service manual.
As briefly as possible. Slip the TV Cable housing into the bracket and snap it into position. At the end of the housing you will find/feel a plastic sleeve that feels like it has teeth or ridges on it. You will also see a "D" shaped button on the housing. Depress the button, and it might fight back, and with it depressed, push that sleeve all the way into the housing until it can go no further. BE Sure you have it bottomed out. Now pull the cable out of the housing and attach it to the correct pivot, the bottom one, on the carb throttle lever.
To set the tension, With the Engine Turned Off, Rotate the the Throttle lever to completely open the butterflies; You Want Wide Open Throttle, aka WOT. What will happen when you do this, is that the sleeve that you pushed into the housing should come sliding out and should also automatically stop at the correct position giving you the correct adjustment for the TV cable. Put the air cleaner on, do whatever else you need to do to go for a test drive, and go for a test drive.
If it is shifting okay and at the correct rpms or points, STOP. You're finished.
If it still isn't shifting correctly, still too early or late, you need to go back to the driveway and go through the whole setup all over again. (BEEN HERRE AND DONE THIS MORE THAN ONCE) If you still can't get the TV sleeve adjustment to cooperate, then you will have to go in and manually depress that D button and move that plastic sleeve yourself. Start with it fairly close to bottomed out and, using a flat bladed screw driver, GENTLY extend it out of the housing one click at a time. you will feel the click when you release the D button and tug on the sleeve. The button grabs the sleeve and locks it into position.
What you are trying to achieve is just enough tension on the cable that you get smooth shifts on time. To get there you have to sneak up on it meaning that you start with a slack cable and the sleeve completely in the housing and advance the sleeve a couple of clicks at a time, as many times as it takes to get the tension right. That correct amount of tension is totally subjective and it will be the transmission that tells you if you got it right. If you think you are close but.... looking for just that leetle bit more, then it is ONE click at a time. Too many clicks and you end up with brutally hard shifts that come too early and too quickly.
Me? I went through all this last spring and early summer with a 700R4, there may still be pictures somewhere. And yes it is a monumental PITA.
The plug in on the driver's side of the case?? That is for the converter lock up. There is a wiring diagram posted to my Transmission swap thread by another forum member that really helped. You can live without the lockup, you just don't get the rpm drop in fourth on the highway.