Well I finally found a useful discussion of this problem. Maybe I can add something. I spent a week driving around the Colorado Rockies with a small trailer this summer, and experimented a bit. The Pentastar has more horsepower *and* more torque. If you want to scream up the pass at 60-65 mph, 5000 rpm, the motor will do it, but the temp gauge will visibly climb too. If you keep it out of passing gear, around 3000-3500 rpm, the motor will lug you up just fine around 50-55 mph, and you can watch the temp gauge go right back down to the mid point.
Other notes:
The same thing happens without the trailer
Turn off the AC
Take the winch cover off (I have an 8274 which sits in front of the radiator)
I have never had the temp go up on the trail
I will be looking for aux fans; warped aluminum heads are a terrible thing