Great engines, you'll love it. Sure one might get a little better mileage towing with a smaller motor, but as was said before, will pull a house off the foundation. If you're towing something better to be safe than save a few bucks.
Here's my 94' Ford C350 (1 ton) Centurion (custom 4 door Bronco) with a 460 and auto. Pulls my 22' North River like it's not even behind me.