Loading the trailer correctly is necessary with a Dakota
No amount of properly loading is going to subtract weight, and that's the issue. The car weight is fine, ive towed up to about 4000 lbs on top of a dolley just fine with it, but once you take that 4000lbs and add a 2000 lb trailer to it, you get to the point where you're not as comfortable. Dont get me wrong, ive towed a diesel Ford front end loader on a tandem axle with it (10k or more) but i dont consider it safe, and i dont consider 6k+lbs confidence inspiring. Im not saying it wont do it. 
Minivan would do fine if you tow a car on a dolly, on a trailer, it's dicey, but doable (a V6 one, not one of those I-4 Chryslers, yikes!).
The only way a minivan is dicey is transmission durability. Most of them weigh as much as a half-ton pickup.
And, gratuitously irrelevant 4cyl Chrysler link! http://www.youtube.com/watch?v=78InPT4iqlw&feature=player_embedded
