I have done my share of mountain driving and steep roads. When going up a grade and the truck begins to slow down, manually select the lower gear and keep the rpm in the upper end of the power band, usually around 4k (OHC engines like 4k, it will not blow up). By manually selecting the gear, it keeps the transmission from upshifting every time you let off the throttle for a little dip or flat spot just to have to downshift again when you get back in the throttle. The torque converter is more likely to remain locked when the engine is running at the upper end of the power band, when the truck slows down the computer usually unlocks the torque converter and tries to hold the gear before downshifting, this is bad! Also, for those of us with engine driven fans it also keeps the fan moving more air while at the slower speed.
Coming down, like mentioned earlier, manually select a lower gear, and when you pick up speed use the brakes firmly to drop below the speed you are comfortable at and gradually pick up speed, repeat. This brake and coast method gives them a chance to cool before applying again. If you ride the brakes they will heat up and fade.
At the elevations you mentioned, you will definitely be down on power, just take it easy and you will get there, which is more important than how fast you got there.
