You guys are great. :clapping: I think I have the idea now. A class III/IV hitch can be obtained with aftermarket brand. A tranny oil cooler, a 9" pushing electric fan in front of the radiator can be installed. And for the trailer, a set of brake can be added. And when the factory struts go bad, then Bilstein or Tokico struts will be replaced. So far, I guess that's about the "Towing Package" in the manual. I would save some $$ by using aftermarket parts instead of factory parts.
In the future, I may modify the air intake system, put in the headers and the complete exhaust system to gain some torques. Supercharger or turbocharger is out of question because this truck is for my daily driver so gas consumption is a major issue. I actually used to modify and boost up Honda and Lexus cars so making the truck more powerful won't be so hard.