The 5 to 6 speed conversion is pricey [abt. 1600] but people should not say it is not worth it to you-- your bucks. If you want it, that is your call.
I like the 6 speed because it does reduce the RPM at freeway speed, and that also reduces cabin noise. Does not help mileage that much, but it was worth it to me.
Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.