Superduties with a manual transfer case can be flat towed. I believe this also applies to manual transfer case Rams. You are probably looking at a 6k+ lb truck if it is a F250 or F350 gasser.
My 2015 Ram with 6.4L gas engine weighs 7,200 lbs. It has the electronic shift and can be flat towed four down. Problem is it get about 14 mpg running around and only about 18-19mpg on long highway jaunts. Of course, get the Power Wagon version and it comes with lockers and winch at the cost of a couple mpgs.
I was thinking Toyota Tacoma, but according to Toyota, even with the 4wd transfer case it is not recommended to flat tow.
Another option would be a manual transmission Subaru Forester which can be flat towed plug it gets great mileage. From watching videos and reading reviews, it won't do anything hard core, but with 8" of ground clearance and symmetric AWD, does a good job on ungraded roads and mild trails.