The TV (Throttle Valve) cable is the biggest bitch because it controls the line pressure of the tranny and no one likes setting the damn thing. If not set correctly, it can cause sloppy shifts and can burn shit up with low or high line pressure.
However, TCI has now come out with a constant pressure valve body that gets rid of the TV Cable controlling line pressures. I don't know exactly how it works, because they came out with it right after I built the 700r4 for my '72 C10. So I didn't do a ton of research on it because I was committed to what I had already built. If I were to build one now tho, or my truck wasn't parked, I would definitely look into it.