copied from wiki...

LQ4 (VIN U)
The Vortec 6000, or LQ4, is a V8 truck engine. Displacement is 6.0 L (~366 cu in) from 101.6 mm bore and 92 mm stroke 4.0 inch bore 3.622 inch stroke . It is an iron/aluminum (1999 & 2000 model year engines had cast iron heads) design and produces 300 horsepower (220 kW) to 325 horsepower (242 kW) and 360 lb·ft (488 N·m) to 370 lb·ft (502 N·m). LQ4s are built in Romulus, Michigan and Silao, Mexico.

LQ9 (VIN N)
The Vortec HO 6000 or VortecMAX is a special high-output version of the Vortec 6000 V8 truck engine originally designed for Cadillac. This engine was introduced in other truck lines as VortecMAX for 2006. It features high-compression (10:1) flat-top pistons for an extra 10 hp (7.5 kW) and 10 ft·lbf (14 N·m), bringing output to 345 hp (257 kW) and 380 ft·lbf (515 N·m).

and the baby 4.8...
The Vortec 4800 LR4 is a Generation III small block V8 truck engine. Displacement is 4.8 L (~293 cu in) with a 96.01 mm3.78 inch bore and 83 mm 3.27 inch stroke. It is the smallest of the Generation III Vortec truck engines and was the replacement for the 5.0 L 5000 L30. The LR4 produces 270 horsepower (200 kW) to 290 horsepower (220 kW) and 285 lb·ft (386 N·m) to 305 lb·ft (414 N·m), depending on the model year and application

 

thank you sir