Well, I researched the answer to my own question. I'll post here so if anyone else needs the info it'll be here to search for.

The 799 heads are in fact an LS6 casting. They list part no. 12564825 for the 01-04 LS6 engines and the L33. "The L33 takes its cylinder heads from the LS6. Originally developed for the Z06 Corvette, these heads improve airflow in and out of the engine. With their pent-roof combustions chambers and new flat top pistons (the pistons in other Gen III Vortec 5300s have a slight sump in the piston deck), the L33’s compression ratio increases from 9.5:1 to 9.9:1. This increase improves the engine’s volumetric efficiency yet still allows it to achieve full power with regular grade gasoline." They have a D shaped exhuast opening. The heads have a 65cc combustion chamber and a 210cc intake runner.

The L33 also has a higher lift factory camshaft checking in at 0.482" for both intake and exhaust with the 1.7 rocker. It is also interesting to note that the L33 has a polymer-coated piston to enable tighter bore clearances and reduce piston motion. This coating also reduces cold scuffing and engine noise.