When we started out in 1999 pulling our 32' Terry I could not afford to buy a new tow vehicle. I was towing with a 1975 F250 2wd regular cab with a 360 4V and dual tanks. Pretty sure it had the C6 transmission. The previous owner towed a car trailer with a 69 Camaro around the Southeast.
I added a trans cooler, new shocks all around with overload springs on the rear. Trailer weighed about 8000 (guessing, never had it weighed) with an estimated 1000 tongue weight. I have no idea what the load carrying capacity of the truck was.
If I stayed on flat ground in Florida it did fine, but it certainly hated hills. It would downshift to second gear at the least incline and slow to about 40 mph going up a good grade.We made two trips to the mountains in NC without issue but it was while knuckle whenever a truck passed me on the interstate.
Third trip up I blew out 3 freeze plugs just south of Atlanta on a Sunday and lost all the coolant immediately. Monday we went out and bought a new 2000 F250SD V10 and wish I had done it earlier. I still have the 2000 today.
You can probably "get by" if you are level when hooked up, stay on flat ground and keep your distance. I don't know what your tongue weight is but I am guessing it is at least 600-700 pounds that you will be adding to what the van can carry. Take it easy, enjoy your trip and even though you love the van, start saving for a new more suitable tow vehicle. Look what Lucille Ball and Desi Arnaz pulled with a 1955 Mercury in the movie "The Long Long Trailer"