We wound up with an F150 Ecoboost. Gear ratio somewhere about 3.92, I think, and high torque. The payload rating on the doorpost is about 1400, I think - it's late and it's been a long day and I'm not remembering all the numbers - sorry. I'll look them up and post them tomorrow.
Anyway, we feel a lot better about our ability to tow our trailer. We aren't planning any off-road trailering - we're sissy campers and like our hookups. Our plan is to do a short trip about once a month, maybe a few days exploring the area, and a longer one - a few weeks - every year. So I think this will work out well for us, and we have a beautiful dark red truck to drive around town.
Thanks to all for your generosity in sharing all you know. We appreciate it enormously - my husband laughs because I won't make a move without asking "the guys." You've all been invaluable.