I'm over at expedition portal as well, have been for some time, great site.
I wouldn't doubt if you were advised to go with a 10,000# rig, you could shackle to a tree and pull someone else out.
However, I don't need to be the big dog, and every time I got stuck it didn't take that much to get me going again. I just don't drive in a 3 foot mud pit! Usually it's a simple straight line pull. but use the chart AstroWll linked to.
I think a 2,000# pull is usually enough to get my loaded F-150 rolling, my Astro is lighter than that truck.
When another vehicle lends a line for help, I doubt they pull more than 2 or 3,000 #, after all, you're not lifting the van, just pulling it. And what are you stuck in?
I got stuck more often in a Baja VW, I'd just get out and lift the front and head in a different direction, haven't been "that" stuck and don't plan on it......but, if I do with the van I think my little ATV winch at 2,500# would probably do the job, while driving too. It hooks into my hitch receiver.
I know the safety, shouldn't be trying to drive a recovery vehicle while using a winch, that cable could break and come through a windshield giving you a new face, just make sure you cover the line with a blanket or heavy tarp, I'll take that chance in a pinch.