Don, good on you for getting back into biking. I hope you have done one of the safety classes. As long as you keep up the oil changes and valve adjustments, that bike should run 70 MPH all day long. The SOHC 400/450 are counterbalanced. That makes them the smoothest of the Honda Twins. LongDistanceRider has taken his SOHC all over the country, abet mostly on secondary roads. He has made some sensible suspension upgrades. You might think about adding a windshield. It will add a lot to the comfort, especially at speed.