Amarillo to Sikeston
Like you, I like to avoid interstates as much as possible. Last summer we ran US 60 from Amarillo to Sikeston MO in a Class C towing a Wrangler. I do not recall anything that would keep you from going this route. From Springfield to Sikeston, it is all 4 lanes. I recently read that the US 60-62 bridge at Cairo is closed for structural problems. I would not recommend it even if it is open. It is very narrow, check it out on Google street view. I use I 57 to IL 37 to 169 to connect with US 45.
In Pawhuska OK stop at the Pioneer Woman Mercantile. In Sikeston MO, Lambert's is a great place to eat. We stayed at Hintons RV park there. Lambert's has a shuttle that will come to the campground. The shuttle driver took us to the side door and seated us so we did not have to wait in line.
2016 Minnie Winnie 25 B
2017 Jeep JKU Wrangler