I've only ridden US-50 through western Missouri, but it was fine. Four lane divided highway, but with shoulders most of the time, it's the easiest (read: no turns to miss) way to get from Kansas City to Sedalia. A lot of truck traffic, but also ran into a few cyclists who regularly use US-50 for training rides who were very helpful in advising about which parts of the highway had no shoulder - though of course I plowed straight ahead without heeding those warnings.

Beyond those 60 or 70 miles, though, I have no idea.