Looking at the different roads on Google Maps street view I don't think there should be a problem. The time and distance seems to be workable and not too much. I rechecked the RV parking at Mt. Rushmore and it looks fine to me. https://www.google.com/maps/place/Mo...5cc641!6m1!1e1
Working on finalizing my summer trip and we are looking at adding a stop at Mt. Rushmore on the way back from Glacier NP.