You will not be able to use that factory installed hitch. I have a similar vintage High Country and I don't put "anything" on that hitch. I have a hitch and ball on it, mostly so it can drag the ground if I go over low spots or dips, so the hitch will drag and not the bottom of the camper on the tail end.
If you want a suitable hitch, then as Theunz stated above, go to a welding shop, or a company that sells utility trailer and have a proper hitch installed.
Note also, you will need to have proper turn signal and brake lights working on the trailer, AND your state will probably require title, registration, and tags for the trailer too.
And one more thing, you need to make sure that "double tow" is legal in your state before committing to the install and purchasing the trailer AND if your state requires brakes on the trailer. Some states require brakes if the total weight of everything combined on the trailer is 3000 pounds or more. Some states may require brakes on anything, regardless of weight.