What's the best route to take, from OKC to Mt. Rushmore?

I've been there once, about 13 years ago when I was working in Minnesota. I've never made the drive from OKC.

Looks like there is no "direct" route, just lots of 2 lane highways to choose from.

Who here has made the trip, and which route is the best? Highest Speed Limit?



Also going to spend time in Deadwood. Plan on seeing Devils Tower, Sturgis & the Badlands.

Any advice pertaining to route and/or sites to see, would be appreciated.
Thanks