My 95 has 217,000 on it, and I bought it with 93,000 on it. A year ago I bought a 2000 with 86,000 on it. The 2000 with 3.73s and 4R100 handles my 10k plus 5er better than the 95 with an E4OD and 4.10s.
These both have much better power to weight than any semi that is fully loaded. Either of these auto transmissions are better than any auto Dodge offered at the time also. They are not that bad. I did have to have my 95 tranny rebuilt at around 163,000, and it had a goose neck ball in it when I bought it, so it has towed all its life.
They do not have the power of the newer diesels. They also aren't stressed as much. I would definitely add a triple clutch torque converter. Any more than that is hype for these engines. I own the equipment to rebuild torque converters, and built the one currently in my 95, so I see the differences inside them.
Sorry for getting so long winded, but buy it, it will handle the mountains just fine. I live in the Black Hills, so every time we go fishing for walleyes, I am pulling grades.
Both ways. In the snow. Against the wind. GBG!