Welcome to the forum. Here's a short primer and then some recommendations.
First of all, the common term "equalizing hitch" actually refers to what is best called weight distribution hitch.
So, what is a weight distribution hitch?
A weight distribution hitch consist of two parts. The first part being the receiver hitch that is mounted to the frame of the tow vehicle. The receiver hitch has two weight ratings, one is weight carrying and one is with weight distribution. Weight carrying is the weight that the hitch can safely tow with a standard ball mount and ball. The weight distribution rating is the weight that can be towed with the addition of a weight distribution package.
The weight distribution package pins in your receiver hitch and then two spring bars are attached to the camper and the receiver hitch. There are several manufacturers and methods used but all have the same simple principal. To distribute the weight evenly throughout the tow vehicle and the towed vehicle. Be sure to consult with and RV professional regarding the installation and operation of the proper weight distribution package as well as any other hitch accessory.
So, basically you are using a WDH to get from this the first illustration to the second illustration......
What hitch to buy?
Get one with sway control built into the hitch.
I like the Equal-i-zer from Progress Mfg. Its a very common hitch as it has been around a long time. (Do not opt for the less expensive and less capable E2 hitch from them).
I also like the Reese Dual Cam and many folks here have used it successfully.
I don't think you can go wrong with either of those two.
Then there's Blue Ox, Andersen, and Husky. Many people like Blue Ox, Andersen is fairly new and has had mixed reviews (some love it and some have had problems), and Husky has been around for awhile but I'm less familiar with them.
Propride and Hensley are the premium hitches. Many say its worth the upfront cost as they eliminate the chance of sway while the others listed above do their best to mitigate sway and control it when it happens (but they do not eliminate it).
Here are some specs for your trailer (Model 318BHS)
- Base Weight7,948 lb. (3,605 kg )
- Hitch Weight840 lb. (381 kg )
- Cargo Carrying Capacity1,655 lb. (751 kg )
- Exterior Length35 ft. 7 in. (10.8 m)
So, this trailer will weigh up to 9,600lbs fully loaded.
You cannot know exactly just by estimating but its the best you can do right now. (You will want to weigh at a CAT scale once you own the trailer).
At 9,600lbs, your approximate tongue weight needs to be between 960 to 1,440lbs, which is a range of 10-15% of the fully loaded trailer.
You will be better off in the 13-15% range in my experience and that would give you a TW of 1,250 to 1,440lbs.
This indicates that a 14,000/1,400lb Equal-i-zer hitch would work (but that is my guess and maybe others with the same trailer can chime in on the size needed).
They cost about $550 for the hitch. You should call them at (800) 478-5578 to verify what you need.
You will also need to buy a shank and a ball, of course. You can install yourself if you own or borrow a really big torque wrench or buy the hitch and have the dealer install it.
Hope this helps you.