Just for info.... my '98 came with a 117A alt. and did NOT come with the tow package and my neighbors '99 does have the tow package and has the 160A alt.

 

you will see tranny cooler lines no matter if you have tow package or not. they go to the tranny cooler in the radiator. if you need tires unless you are going to change the gear ratios go back to the stock tire size, it will help you for the hills and surprisingly economy if you dont try to be a speed demon. and if you change the rear end gears you must also do the front gear unless you will NEVER use 4x4. if you do the rear but not the front then remove the front driveshaft so you an use low range for trailer manouvering purposes and so you dont blow something up by forgeting to not use 4x4. '98-'99 didn't have electric fan did they? might be worth looking into an electric fan setup.