The new(er) Ford 3" hitch receivers have a 2100lb hitch weight rating, without a wdh. Even a 48" extension would allow you over 500lbs and still be within the mfgs ratings. Without suggesting you exceed that, if you're only towing up to a 5000lb trailer, I would make full use of the best OE hitch offered on a pickup truck and just get a stout section of 3x3x1/2" HSS, drill 2 holes to pin it into the receiver and 2 more to insert a 2" hitch into the extension, fab up some safety chain hooks, either welded on or clamped on and call er a day.
Depending on the trailer style/tongue length, you could get by with as little as 36" extension.
In short, I wouldn't junk that stout of a hitch for your intended use.