Not very scenic, pretty heavy traffic, headwinds.
Actually, you should head NW on NEB 2 out of Crawford up to SD -
Then zig to Hot Springs and get on the Mickelson Trail all the way to Lead.
(Personally, I'd skip Mount Rushmore and the crowds.)
The Black Hills will be a welcome, cool relief.
From Lead take Spearfish Canyon/US 14A to Spearfish and Bell Fourche -
Then take SD 34, WY 24 over to Devils Tower - super nice ride and stunning vistas.
From Devils Tower you can cut down to Moorcroft and Gillette to Buffalo.
It's the difference between a cardboard cutout of Elvis and the real thing.
You can always head south from Yellowstone to Grand Teton -
Then either cross Teton Pass (steep) or ride the Snake River Canyon into Idaho.
From there you can cross over to Arco, Challis, and Stanley.