As someone that has pulled a 1966
Overlander for 10+ years, I would suggest just a standard Draw Tite hitch with a sway bar attached. I pull with a Ford Excursion (basically a 3/4 ton) where you will be pulling with a Ford Expedition (basically a 1/2 ton). My guess, 800lbs bars should do you well regardless if you are running with a full tank of water up front (30gal. x 8.35lbs= 250lbs) or not, you might just need to go up another link on the chains since you're running with a 1/2 ton not a 3/4 ton. This will allow the rig to be flexible, yet still ride level. Be sure to understand setting up the head pitch when putting all this together since that is the key along with the bar size to a soft, yet level tow/trailer going down the road.
If you have not replaced the axles, I'm sure you need to do so based on the age alone. When replacing mine, I went with the stock 22.5 degree down angle with 7.00x15 bias ply tires which gives the trailer a great height and ride since it's a slightly stiffer side wall and a 29+ inch (uninflated) tire in height and you won;t have to worry about drop hitches, etc....
Hope this helps, if not, someone smarter than I will have to step in.