Ahh Yes!!!
I know the plate you're talking about. On my 2001 it was under the pass. side seat under the carpet/flooring mat'l. on my 2002 it's mounted on the radiator core support right side upper.
It just has the various codes for paint,trim,axles,interior and engine/trans combo. The codes for engine/trans are just three letters for each denoting whether it's a high output ETH or standard ETC engine. If it has a 6 speed it'll have the DEE code stamped there as well. I don't think the VIN number would tell anything except that it has the Cummins engine in it. The glove box also has some stuff like this on a printed sticker attached to the bottom of glovebox.
Phil