I had a 01 Jeep GC that was rated to tow 6800 pounds (V8.) My old boat and trailer weighed in right around 4000 pounds but, was like a sail in the wind behind the GC. I sold it for my Yukon and it was night and day different. The boat and trailer didn't pull the truck around, it stopped better and I felt much safer towing.
Yes, my GC towed at 70 MPH but, after purchasing my Yukon I would never go back.
What does the horse and trailer weigh together?