I saw one up close in the Keys over Christmas. They appear well built to the same standards as their big trailers. They are not a retro look though, if you are looking for that. Have no idea how heavy they are either. This one looked pretty good considering it was probably 6 to 8 years old.
Edit: in the pictures of the units for sale, one has a picture of the plate with the GVWR rating - it says 3250 lbs. So this could be pulled by nearly any B van, including the Promasters.