I have a 1983 Trek 620 with original components that I do not use for touring - although I originally thought I would. I live in the western US. The reasons I do not use the bike for touring are because of braking (not strong enough downhill - even if unloaded) and downtube shifting (not smooth). Some of the problems you experienced will be amplified in the mountainous west.
I bought another bike that is a great touring bike, so I will never use the Trek for touring.
I am getting rid of many of the original components on the Trek and going with 700c, brifters, dual pivot brakes. I'll probably use it for sunny weekend rides with the family.
Not sure if I'm helping you, but that's what I have to say.