I certainly can't help with route, but can comment on limiting yourself to 50mi/80km days-this would be wise. Without knowing your fitness and how much riding you will have done prior to trip both loaded and loaded with a lot of climbing per day, starting off with some easy days in the 40mile range is always a good plan. I've found this to be the case with any trip, if possible, but if you are dealing with lots of climbing from the get go, I'd recommend it.
Only you can know how a given distance will be with a given load and a given amount of climbing, but if you aren't able to do much loaded riding like this beforehand, starting out with shorter distances is always nice.
I've ridden loaded in mountains when I was fairly fit and in days with 2000+ meters/6000+ ft climbing per day, at times did 30-40 miles per day (50-60km) depending on where places to camp where/towns or whatever.

again, only you will know what works for you, but I don't think my experience is that unusual as a reference.