There was no LS model in 2007. Here is what Edmunds said about the different trims:
Regular cabs can be had in base Work or midlevel LT trims, while the extended and crew cabs can also be had in plush LTZ form. The Work trim comes with the basics, including air-conditioning (extended and crew cab versions), a trip computer, OnStar telematics, vinyl seating, a 40/20/40-split front bench seat and a tilt steering wheel. The LT trim actually consists of two subsets, 1LT and 2LT. The 1LT adds deep-tinted windows, chrome grille trim, alloy wheels, a CD player, cruise control, full power accessories, cloth seating, keyless entry, an auto-dimming rearview mirror and a leather-wrapped steering wheel. Opting for the 2LT nets you dual-zone automatic climate control (in extended and crew cabs), front bucket seats and steering-wheel-mounted audio controls. The top-shelf LTZ has all of the previous equipment plus rain-sensing wipers (with heated washer fluid), a Bose audio system with six-disc CD changer, keyless entry/start, leather seating, an exclusive dash design with wood/metallic accents, 12-way power and heated front seats, rear audio controls and Homelink universal remote.