As Shenel posted It depends on your tongue wieght and type of hitch. Generally I find that trailers over 3500 lbs should have a weight distributing hitch. When hauling a 4500 lb TT with the WD hitch my 83 F150 would drop about 2 to 3". My 4500 lb fifth wheeler has a pin weight of 800 lbs but it is directly over the axle and only drops it 1.5" on my 95 F150. Both trucks were equiped with HD rear springs. My 95 4.9 with 3.08s hauls very well, better than the 83 302 with 3.55s
Check your springs and hangers for broken leaves or rust damage.
Good luck and be safe