It would seem that you are comparing the LBZ with LLY's built prior to 6/1/05. It is my understanding that all LLY's and LBZ's built after 6/1/05 have the same compression ratio 16.8-1.
GM through their press releases gave the impression that they were different, however it seems that the 06 LLY was a detuned LBZ for the purposes of giving them time to evaluate the 6-speed Allison and or something to brag about for the new model year.
Apparently the part number for a dressed 06 LLY or LBZ motor is the same as is the part # for the ECU
If you read the GM press release here
http://www.dieselplace.com/forum/showthread.php?t=67521 you will see that they mention a significantly revised motor
"The 2006 Silverado
HD and Sierra
HD with the Allison 6-speed automatic transmission will be equipped with a significantly revised 310 horsepower DURAMAX 6600 (LLY) through the third quarter of 2005. It will be replaced in these applications in the fourth quarter of 2005, by the higher output, 360-horsepower DURAMAX (LBZ).
They dont say it's a different motor, in fact further down under the specifications
"2006 DURAMAX 6600 Specifications (LLY,
LBZ)
Assembly site: Moraine, Ohio
Applications: Chevy Silverado and GMC Sierra 2500HD, 3500 pickups; Hummer H1, Chevy Express and GMC Savana full-size vans; Chevy and GMC medium-duty trucks
Type: 90º V-8 charge-cooled turbodiesel
Displacement (cu in/
cc): 403 / 6599
Bore x stroke (in x mm): 4.06 x 3.9 / 103 x 99
Block material: cast iron with induction-hardened cylinder liners
Cylinder head material:cast aluminum
Intake manifold:cast aluminum
Exhaust manifolds:cast nodular iron with steel pipe extension
Compression ratio: 16.8:1
Valve configuration

verhead valve, four valves per cylinder
Valve lifters:Mechanical roller
Firing order:1 – 2 – 7 – 8 – 4 – 5 – 6 – 3
Fuel system:direct injection diesel with high-pressure common rail"
They make it clear that they are the same with different outputs. The higher fuel rail pressure is common to both and is more related to emissions than output in this case.