If considering a Nissan, make sure you double check the receiver capabilities. I believe I have seen discussions that there isn't anything on the hitch, but that the owners manual limits tongue weight to something like 1000# or less.
With a trailer that size, you will need over 1000#. Our last trailer had a GVWR of 7200# and the last time I scaled it I was pushing 1200# tongue weight. Nice thing about the Express (and I would assume the Econoline) is that you can get hitches with tongue weight ratings of 1500# or more.