To verify which series you have check the VIN# of the truck. The 8th digit is the engine ID and it will either be a 1, 2, D, or 6.
01-04 LB7 is a 1
04.5-05 LLY is a 2
06 LLY is a 2 (uses same mods as LBZ)
06-07 LBZ is a D
07 LMM is a 6 (new body style GMT 900 series)