I believe what you see is what you're are going to get...
I spend a great deal of time in the Rockies, I find that I slow the vehicle speed and manually downshift to keep rpms high (3500-4000). I turn on the four way flashers, and enjoy the ride.
In the photo, I am climbing eastbound on I-70 at the Eisenhower Tunnel summit, Elevation, 11,200 ft. (west of Denver) . Note the four way flashers are on. the transmission is in 1st gear, Speed is about 25 mph, and the rpms are at 4000.
2001 Coachmen Mirada (Ford F53 6.8L V10) - Toad 2001 Civic
It won't do MACH 2, but I can get a sandwich and take a pee.