A 2500 Express chassis will handle it.
If it's the 4.8, it'll work hard at it.
My concern would be more hooking a 6000lb + trailer to an older vehicle I had no history or experience with and hoping to make it.
Idk if uhaul dollies are the same, been years since I used one, but last one was too narrow to haul a 1999 Ram 1500, but a 1990s Chevy 1500 fit on it tightly. Based on that, your guess that the track width of the van being too wide is likely accurate.
And uhaul is sometimes sticky on what they'll allow you to use as a tow vehicle and in my experience they won't rent to you if your trailer light hookup doesn't work. (I showed up with Chevy K2500 454, 4x4 once to rent a dolly to tow a 4 runner and they turned me away. Came back with a F350 dually cab n chassis from my construction site and they then "allowed" it.
Also got snubbed pulling in with a K1500 GMC, told them I was towing a civic (was planning on towing the GMC or the Ram 1500) and had to go borrow a buddies 3/4 ton to get it off their lot.
So check that before you make the trip.
As far as tow ratings etc, there's rvnet and there's the real world and lots of things get towed just fine that don't pass muster on this discerning site.
