Except nearer to the main cities and towns, there aren't many 4 lane roadways. Your best bet will be to try to stay on the Trans Canada (104/105) as much as possible, as it should be a bit straighter and less challenging for a big rig. If you get sidetracked and off on any of the "Cabot Trail" routes, you'll enjoy the scenery, but perhaps not the drive. I would try to stay on 105 between Port Hawkesbury and North Sydney with a large/long setup. I haven't driven the roads on the rock yet, so can't comment on them.
