I towed my old XJ on a 18' Kaufman w/ my 01 WJ Limited... I did have bags inside the rear coils (Isuzu Rodeo bags actually), New Factory Up-Country coils spings all around, Addco Swaybars, and a Tekonsha P3 controler...
Also the WJ had the factory tranny and ps coolers.. D44A, 3.73's, Class IV hitch, intake, etc... Oh and my trailer had brakes on both axles... It did just fine towing back/forth to Mtn. City, etc... I'd do it again if need be and set up properly. I never was scared once...
W/o airbags, a equilization hitch, swaybars, coolers I wouldnt even try it... Stock the amount of tongue weight you're going to need is going to completely make it undrivable (atleast IMO)...
The XJ + gear + Trailer weighed in at 6650lbs.