All depends on what you call a hill, the ones around Toowoomba etc are just bumps, while I call hills around Tumbarumba proper hills and a pain to tow, we always travel the Melb run using non highway routes, I hate the highways, from Dubbo to Gold Coast I would go Dubbo, Dunnedoo, Coolah, Gunedah, Manilla, Warialda, Texas, Inglewood then just barrel along the Cunningham Hwy to Warwick and onto GC.....you could run the Bruxner from Texas thru Tenterfield then down thru the hills into Beaudesert and Canungra to the GC but some big bluddy hills thru Canungrs but no trucks......using the Cunningham Gap isn't really a biggie, just use your gear box, its just a long slow downhill run.
The roads mentioned to Inglewood are great runs in a van, buggerall trucks and its a nice easy hassle free drive with quite a few nice places to stop.......you may need more time as places like Bingara call out for a long stop to check out the place.