I was able to pick up the sub-series of these GMT K2XX series from Wikipedia:

https://en.wikipedia.org/wiki/GMT_K2XX

GMTK2RC: Regular Cab Chevrolet
GMTK2EC: Extended Cab (as known as Double Cab) Chevrolet
GMTK2CC: Crew Cab Chevrolet

As so on...

http://imcdb.org/vehicles.php?make=Chevrolet&model=GMTK2XX&modelMatch=2&modelInclChassis=- on