It was "somewhere" around 02/03 that the GEM disappeared and it's functions were absorbed into the instrument cluster and other modules... I can never recall and prefer to look.
Easiest way to tell if your truck has a GEM is to look at the fuse box under the dash.... If this fuse box is taller than it is wide, there will be a GEM attached to the back. If it is wider than it is tall, it wont.
HTH