A 4.0 Ranger with an automatic and 3.73 gears should handle that trailer adequately, although a little slow by today's standards. As a point of reference I used to tow a 21' ultralight (3100 lbs dry, 4000 lbs road-ready) with a 1994 Aerostar with the 4.0/3.73. It maintained 60-65 mph easily on the freeway, pulled passes at 45-50 and averaged about 12-13 mpg towing a heavier but a little more aerodynamic trailer. I would expect similar results in your situation. The only caveat is that I wouldn't want to tow long distance with no trailer brakes.
