State Fair Time, St. Louis, Mo to Des Moines, Iowa

Going to the Iowa State Fair in August.
Will be pulling my 29ft 5th Wheel, on my 2005 Duramax Diesel.
What is the best way to go ?

70 to 35 ?
70 to 63 to 163 ?
70 to 65 ?

I know it takes me almost 3 hours to go 150 miles, driving 63 MPH.
All 3 Routes about the same Mileage, and Time.
Thanks