What is the best balance between towing capacity and MPG? I am confused about all the model types 2wd and 4wd, V6 vs V8, etc.

I am looking to get a T4R and I need to pull a 3500 lb boat/trailer a few times a year. No great distance but I also want a good daily driver for my normal commute. I will be replacing a Volvo S80 and my old Jeep Grand Wagoneer.

You guys know best, so any recommendations would be greatly appreciated.