I too tow with an 07 Tundra (5.7l) pulling an 25' International FB.
I just took it out again about 2 weeks ago in the Rocky Mountains (Breckenridge, CO). The truck did marvelous! I seriously averaged 14 MPG the whole trip (about 90 miles) to my Denver suburb home.
Regardless of the trucks payload capacity, I do use an equalizer weight-ditribution hitch.