Merriwa to Scone is OK. Merriwa to Willow Tree is now tarred. You will hit some dirt going from Kingswood (south of Tamworth) to Nemingah. Go into Tamworth and turn right at the second roundabout will take you to Nemingah via a tarred back road.
Some of the roads around Ashford to Warialda can be a bit rough but are all tarred.
Lots of flat straight roads past Walgett, just watch for goats at any time of day.