I am assuming you don't have a copy of the 2004 sales brochure, which has this information in it.
The Laramie has certain features that you may want, or not want:
(1)dual zone air conditioning vs. regular on SLT. In other words, if the passenger wants more or less AC, you need to adjust the vents on the SLT manually; (2) fog lamps (actually driving lights, as they are white not yellow)are std on Laramie--optional on SLT; (3) chrome side bars on grille (SLT has black background); (4) HomeLink; (5) light group (optional on SLT); (6) flat load floor on quad cab (optional on SLT and included with leather in SLT); (7) auto dimming rear view mirror (optional on SLT), (8) chrome side moldings (black on SLT as option); (9) power adjustable pedals; (10) power outlet in business console; (11) silver interior accents; (12) power seat (optional on SLT); leather seats (optional in SLT but apparently with different center panels--"preferred suede" on Laramie; (13) security alarm and sentry key (optional on SLT); (14) 6 disc CD (optional on SLT); (15) steering wheel audio controls and Infinity sound, (16) leather steering wheel (optional on SLT individually or included with leather seat); (17) front seat center cushion storage (optional on SLT with leather or premium cloth power seat); (18) electric shift transfer case (if 4x4); (19) sliding rear window (optional on SLT).
In summary, many of the features of the Laramie can be ordered separately as options on the SLT. A few things such as chrome grille bars, silver interior accents, electric shift transfer case, or leather seats are things that some folks DON'T want, so they might prefer to start with the SLT and specify the options they want.