Bdkhoops, realize my reccomendations came with an aire of caution based on my perception of your experience/skill towing, as well as having lived either in or near the Rockies, Cascades or Alaska range for 20 years now.
Of those 3, the alt of the Rockies sucks the life out of naturally aspirated vehicles.
Coming downhill is the same anywhere.
I'm serious when I say I've towed that much or more with a half ton.....in the mountains.
But I've been wrenching on trucks and trailers and towing stuff way scarier since I was 15. Got scolded at work for loading up 14-15klb trailers and pulling with my F 150. That move finally got me a bigger company truck though!
I don't know what all your navigator has for payload, towing package, can you upgrade suspension or does it have air ride, care to buy new tires or does it have heavy load d or e tires, etc.
You can modify a bunch for suspension but not much you can do about horsepower except go slow up hill.
I just know you got a lot of cargo and I've done a similar load, lighter trailer though, behind an Expediton. Yes it would have made it x country, but I was glad it was only a couple hundred miles.
You could make it a more capable rig if you're not worried about factory ratings, albeit some are more important than others, or $20k would get the job done or close at least for a heavier duty tow rig.
Another suggestion, do you know anyone with a similar size high profile trailer? TT, cargo trailer, Sno machine trialer etc that you could load up and do a good test drive with? That would give you an idea of what to expect without a car full of kids, a weeks groceries and reservations at the campground all hinging on the success of the trip. If you were closer I'd let you hook up my 32' sled trailer and see what ya think.
