I believe it's just a trailer hitch and trans cooler, but I think they all came with the trans cooler. Maybe heavier rear shocks. In the late 80s, maybe 88 and 89, the towing package meant it had the desirable Dana 44 rear from the factory.
I think all the AW4 autos came with the cooler piped thru the radiator. Maybe the tow package had a remote mini-cooler also.
I really have no idea about the tow package, but maybe slighty larger sway bar and a 4-prong connector?