Few things to clear up here. For starters there was no VZ GTS. You probably mean the Clubsport, and the LS2 sounds a whole lot sweeter then the LS1 i agree.
The 6 speed auto isnt a ZF its a GM unit, the 6L60E, which although isnt quite as good as the ZF is still a mean gearbox.
Im sure it isnt the "technology" thats preventing Holden from putting out 350 kw. I mean they could do a simple edit, but thenn theyd have emission problems etc, plus there wouldnt be a lot of headroom for a future power path. Holden also doesnt use SOHC, they use OHV (over head valve), the SOHC Ford is the 220kw version in the ghias, and theyre pretty crappy. The DOHC engine is used in the XR8 (not FPV) and the GT and GT-P