Just about any B built on the Chevy Express 3500 with 6.0 V-8, provided it has an adequate hitch bolted to the frame. This combination has a high enough GCWR that there is about 6000 pounds towing capacity left when the van is at maximum loaded weight, which is often the case when you build a house inside the van and load it with your family and traveling stuff. Chevrolet rates "towing capacity" as 10,000 pounds but that is for an empty van.
Not all B manufacturers use the 3500 or opt for the 6.0, as the Express 2500 and 4.8 V-8 usually show slightly better MPG and cost a little bit less.
Some models of the Sprinter van have 5000 pounds towing capacity, others slightly less, so it depends on which van was used to build a particular model of RV. Daimler-Benz usually rates "towing capacity" as excess of GCWR over GVWR, rather than the GCWR over curb weight used for most passenger vehicles and light trucks in the U.S., so that 5000 is real.