better flow will improve milage and a good air filter helps.
if you keep you fuel filter clean too
also change your oil regularly or a bit more often when the oil starts to get old& black the engine works harder. also transmission oil cgange /flush wouldn't hurt.
change the transmission to a 700r4 it's got over drive.
different wheel size, air dam.
keep the tail gate down for less drag.
but really how much do you think it's going to cost to do all this?
parts, time, labor all add's up
you can buy alot of gas for all that.
lets face it you bought a truck. not only a truck, but one with a v8
v8's are not exactly known for good gas milage.