I had a buddy towing a 21 Four Winns Liberator with a Jeep Cherokee (4.0 liter). He had to have the WD bars or the Jeep dragged it's bumper and swayed badly. He added these bars and everything was awsome!!! He sold the boat, but may still have the stystem, I'll ask him. I've never seen such a dramatic change in towing. From scarry to perfect in a couple of hours. But as stated, the system wasn't cheap. Required a new draw bar and the attachement for the trailer tongue. But like I said, night and day difference. Oh, and this was a surge brake trailer, so yes, you can get a system that works with them. It's the Equalizer system. They have a web site.....
Before I spent a lot of money, I'd add tongue wieght as stated above and then give it a try. New tires in the trailer too.
O.K......I just talked to him. He still has the entire system. It's rated for a 6000# towed wieght, so it will work for you. He has all the instructions and all the parts. Paid just over $500 for it new a few years ago. He'll let it go for $200 if you're interested. Gimme a call, 616-540-1224 if I can help.