Many rigs your size go up and down the Alaska Highway. Best advice I can offer is to not use the posted speed limit as a guide. Go slower. Don't set a strict schedule, let there be flexibility so you can take your time and drive to the road conditions.
This past summer, broken RVs were common between my place and Whitehorse. Broken hitches mostly. The frost heaves were bad, the potholes were nasty. Just drive to suit the conditions so you don't abuse your rig.
When we're towing the fifth wheel, we tend to drive 10 mph below the posted speed limit and don't hesitate to take it down to 30 mph through the rough areas. In my car, I whip along quite a bit faster, usually more than 10 mph over the speed limit.
Once you're north of Fort Nelson (British Columbia) on the Alaska Highway, drive the speed that suits you and your rig.