If you are trying to speed your travel time up on your way back to SC, I would only take US 385 to US 26. Then take 26 to I-80 to US 81. US 81 is a very good four-lane highway all the way from York, NE, to Salina, KS. In Salina, you can choose either I-70 east or I-135 to I-35 to I-40, then east.
We just used US 81 in NE last week and it is far and away the best N-S towing route in southern NE.
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2015 RAM 2500 4x4 crewcab 6.7L CTD; 2016 Rockwood Signature UltraLite 5th wheel