Once you go west of the TX Border, you will find a basic truth: All the "Mountains" you have driven in in TX & East of the Mississippi are REALLY overrated hills
When you hit NM/CO/UT/WY and make those 3% grade climbs for 10-20 miles only to come to the final twisty-turny 7% 10 mile last leg to the crest...THEN you know what a mountain is
You will learn to drive the extra 60 miles to the pass, rather than taking the more direct over-the-crest route
Just go slow and take breaks, keep your truck apps on and watch your tranny/oil/water temps. If you have to pull over a big'n (classified as a 9K or more ;
best do it in the morning, late evening, or overnight if you can. Summertime temps in the high desert can easy be 110 deg with blacktop surfaces being 120 deg.
I have a couple of friends that have similar rigs to ours towed by a F150 EcoBoost; they are not reporting any problems but gas milage is @ 8-9mpg-7 on the steeper grades @ 4K RPM.
(We lived in NM for 10+ years and towed a Coleman Niagra Popup behind a pretty much stock Ford Aerostar minivan - the big popup was probably right at the Aerostar's GVWR-- or over
we did not have any problems in the mountains though)