text: The route designation is a distinct entity from the local road name (to the point where routes are often carried by unnamed roads), but for a historic route often pieces of roadway along its former alignment will be officially (re)named to incorporate the former route designation so you get things like "Old Route 66" and similar.
  
  So I have strong doubts about the road being literally named "Route 66"... I'd say for ways with both names, delete the "Route 66" name in preference to "Heartwood Road" and add old_ref="US 66" if it's not already there. Maybe StreetSide can help