That's an avg of 7000 feet of climbing per 100 miles. I've done two centuries with 1000 ft of climbing crammed into a 10 mile section of it, with the rest flat. A ride like this is hard to imagine. I doubt it would be 20 hours each day, though. you get to come back down the hills, too.
I've ridden in the shenandoah's with 46x18. It allowed for easy climbing and, provided you're okay with ~150 rpm, 30 mph descents.