"So what Im hearing is the throttle cable has worked fine for most, but only a few have had success with the kickdown cable/brackets."

I have run the Lokar throttle cable on my race car for the past 10 years or so without any problems but when I was redoing my 68 Charger last year I went with the Bouchillon throttle/kickdown kit as it was supposed to be the easiest to install. I changed from a 383 to a 440 and the stock stuff would not work(too short).

http://www.bpeusa.com/BPEaccBracket.asp
Pretty expensive but great quality easy to install and kick down works great! It utilizes stock throttle cable and the kick down is adjustable so you can dial in your kick down.
Mike