Do you just enjoy the truck as a hobby, or for fun, or do you use it for carrying capacity? If you just like it, then by all means keep it and enjoy it, but if you have it for carrying loads, then [if you haven't seen it already] checkout the thread on trailer use.
As for mods, the best way to go is air pressure in tires at sidewall max, and then grille blocks work pretty well. Of course you will need extra attention to temperature in the heat, but that brings up the Scanguage or Ultra Guage. I prefer SGii, but to each their own. And of course the main list to checkout,
65+ Vehicle modifications for better fuel economy - EcoModder.com.