Jan and Dick, Barb and I just did I-70 in April, returning to Wisconsin's. My only fears were snowy roads. But it was a beautiful sunny winter day up at the Vail Pass. Was many many feet of snow there yet. The Vail rest area was completely covered by with snow, but it was open and being used. Almost tunnels to get to the door. ☺
But your worried the the V-10 won't be up to the climb. We don't tow, so I don't know how that effects it, but by itself, that engine pretty much plays with this coach. We love mountains, so we are always ether going up or down somewhere. Many inclines much worse than the interstate system. Never a concern. Have plenty of power to spare. They put this engine in 30+ class A's, and you know they tow.. Would say you will be remarkably surprised. Let us know, when you return. That's a beautiful drive.