I recommend updating your truck and trailer, and leaving a couple horses at home. And I am not a member of the weight police. I would not try it with less than a 350/3500 dually and a newer light weight aluminum 2 horse trailer, and then I would add suspension upgrades, such as air bags or stabliloads, plus a good hitch with weight distribution, and still you will need one of the smaller campers. There is a lot of difference in pulling a static load like a boat or cargo trailer and a live one. 4,000 to even 5,000 pounds of horse flesh moving about will cause some sway when you go over weight limits. I have been dragging horses around for 50 years.
The best way to accomplish your goal is with a living quarters gooseneck.
