If you are looking at gas trucks:
Dodge, you already know the story.
Chevy: If you can find an 8.1 Liter, in my experience, they do just as good as early 6.0 gas motors, with more power.
Chevy half tons, outside of vortec max/1500Hds are too light, IMO, for pulling more than one vehicle on a trailer. Physical weight, the 10 bolt rear, and the 4L60 trans are all against you. Fine for towing your S10, but S10 + some, hmmm..
The 6.0 or 6.2 1/2 tons would do it. They'll get the same mileage as the hemi. Newest trukcs have 6 speeds which helps. You can run 3.42 gears and still have really low first gears for towing.
Ford, the heavier F-150s would probably handle pulling that load as well. Bigger rear axle than the chevys. Can't get lower than 3.73s, I think, though. 09s are 6 speeds, and much nicer than the 08s and previous, at least to me, and I've driven both.
You aren't likely going to get 17 hwy in any gas 3/4 ton, unless its low to the ground 2wd, and you drive real grandpa-like.
I bet for 3/4s, the 5.7 hemi, 6.0 GM, and 5.4 ford all get just about the same mileage, probably like 12 city, 14hwy or so? Maybe 15. The rear world tests that I've seen don't show it.
If you want a 3/4 ton and a gasser, I'd find an 8.1 Chevy with an Allison trans.
As soon as I can find the cash, I'm getting a 2009/2010 F150 crew with the 5.4 + 6 speed, awesome truck. Plenty for towing my Jeep. With backup camera that can see the hitch, trailer brake controller, all that jazz.