GILSDEAD, welcome to iRV2. Hope you find the site helpful.
First palce I would start is to weigh your van loaded with normal cargo and passenger and a full tank of gasoline. Conversion vans tend to be HEAVY and not leave you with much payload capacity.
Next find in the owners manual, the GCWR (gross combined weight rating) for you specific engne and axle ratio. This is the maximum your loaded van and trailer can weigh combined. Now find the GVWR located on the door jamb sticker. This is the most weight you can palce on the vans two axles.
With this information you can find the maximum weights you can work with and be within the manufacturers rating fro your van.
GCWR - Loaded Van = Max loaded trailer weight.
GVWR - loaded Van = Max loaded trialer tongue or hitch weight.
You should not exceed either rating number.
DO NOT pay any attention to the vans "tow rating" as it is number based on a a base model van, no options, no accessories or passengers beyond a 150# driver.
Visit Ken Lenger's site HERE.
A good discussion on towing terms and weights. He has a spreas sheet to help work through the numbers at the bottom of the page.
Have fun now,