A winch and a selectable rear locker or limited slip, plus some portable traction aides (Portable roads, tire chains, ect) will get you almost anywhere you'd want to take a full-size van anyways. A small lift for a bit more ground clearance never hurt either.
Although I've taken bone-stock Ford E-250s and Chevy Express 2500s into some pretty hairy spots for work, and I've never gotten a van STUCK stuck-the only time where I had to do anything but just keep on the throttle and keep momentum up was when I had to go service a phone tower in Northern BC in the middle of winter after a blizzard, and that just took snow chains and studded tires.
But if you ARE going to take a 2WD van off-road, I personally wouldn't want to take a full-length van, especially not a Ford with that massive rear overhang, I'd be too paranoid about high-centering it.