I just came through there heading north in a 35' 2007 Ford F-53 based chassis motorhome (weighing probably 17k, no tow vehicle either), which has the 362hp/457lb torque V10 & 5 speed Torqshift. I thought I was doing great, maintaining 65 through most of it, dropping to 50 in some places.
In a real steep area I dropped to about 45 and was passed by a 42' diesel pusher pulling a 5000lb full size crew cab truck, he must have been doing at least 65mph. I'm sure he thought he was doing great also.
So enough power is subjective. I had trouble dodging the 40mph guys in the slow lanes, who we're being passed by big rigs going 41mph. It's real interesting through there the right time of day. Other times you wonder why they put in 4 lanes each direction.
Not directly applicable to your question I know, just my recent experience through there...