Big TK,
The only way to really get in shape for walking in the mountains is to walk hills.
Running lifting weights etc are great for going up hills but when you turn around and start going down for extended periods carrying weight there is no substitute for actually working out walking hills up and down carrying weight.
I believe most experienced in shape western hunters will agree it is the downhill that kills you.
Work your way up to carrying a 30 lb pack up and down a steep hill (appx. 45 degree slope). When you get to where you can go uphill 80 to 100 yards and then back downhill 80 to 100 yards for about 1 hour continuously at a good pace you are getting in the ballpark.
Walk hills for an hour 3 days a week for three months before your hunt. Work in at least one day of serious weighlifting and one day of serious cardio (running or biking) a week during the three months and you should be ready. This is for an on foot pack meat on your back hunter public land hunter who want to be ready to cover 5 to 10 miles of rough mountain country a day if necessary locating the elk, and then be ready to backpack it out. If you get to where you can do this workout you will be in great shape, ready for the mountains. This is the workout that works for me.

Some of my friends only run to get in shape and they seem to do just as well in the mountains for the first couple days but then they start to get worn out by the third of fourth day of hard hunting.
If you have horses and/or don' t plan to get more than half a mile from the road then conditioning does not need to be so extreme obviously.
Lots of people shoot elk every year without doing any conditioning at all. Each person knows their own limits, just get in the best shape you can and go for it.
You will have great time either way.