I highly recommend something with a 6 sped transmission. That means 2007+ Tundra, 2009+ GM Twins, or 2009+ F-150. The F-150 I would prefer 2011+ 5.0L or Ecoboost as the 09-10 had some transmission limitations that would drive me crazy.
For any of them, you'll want to pay attention to the payload as well as the specific equipment they have. Some half ton crew cabs have under 800 pounds of payload. Some have tow ratings of 5000 pounds. Specifically, you want the 4.300 axle ratio for Tundra, 3.55/3.73 for F-150 and 3.42 for GM. And the heavy duty towing package for the transmission cooler.
They would all do well. Pick the one your wife likes best. :)
