drsolo,
Your 1992 2500 GMC van most likely has the 5.7 liter V8 and it has plenty of power to pull double the weight of your Wildwood trailer. A slim possibility your van has a smaller size V8 because few of them were ever sold in the 2500 model and usually only in the short wheel bsase version. The unknown is what rear end ratio your van has as that will make a huge difference in pulling ability. Most had the 342 or the 373 ratio as OEM. Yours, being a camper van conversion and the long body version, most likely has a 5.7 V8 with either the 342 or 373. You'd know if you purchased the van new but if bought used, who knows what may have been changed since new. The other power robber is an mostly plugged catalytic converter as your van is now 24 years old. OR the engine cylinders/rings are worn and losing compression.
We had a Chevy 2500 Deluxe Starcraft Van Conversion and had no problem pulling a 30' Nomad Century trailer loaded with options and full water plus all our food and stuff which is more than double your trailer's weight and it had the same front shape as yours which is far from aerodynamic in shape/wind bucking. I could pull the trailer at 70 anytime except up hills or long steep grades.
Have your van's engine checked and the catalytic converter also as it should pull your Wildwood at even 70 mph easily without flooring the go pedal. Something isn't right with your van and will need to be fixed anyway so you'll be paying double plus in the long run by having your Wildwood delivered since the van needs to be taken care of also.
However, remember that your trailer tires have a max speed of 65 mph even if they are 225/75/15 "D" range tires (8 ply rating and 65 psi max inflation) and less than 65 mph if they are smaller tires than those with 50 psi max.
