have you seen what these guys do with LS2s? i was reading their performance packages and i was more intrested in maxing out the engine without having to rebore to it. if i had the money i go for it:

2005 GTO LS2
6.0 L Engine package
490 BHP / 440 lbs-ft of torque
Package includes:

Engine removal, inspection and cleaning for assembly
Lingenfelter CNC ported & polished LS2 cylinder heads
2.02 / 1.57" one piece stainless steel intake & exhaust valves
Three angle valve job, hand blending of valve seats
CC chambers, surface, set spring heights and assembly
Competition Cams valve springs
Lingenfelter designed Competition Cams hydraulic roller camshaft
Modified LS2 oil pump assembly
Lingenfelter ported & polished throttle body
Low temperature thermostat
Corsa stainless steel cat back exhaust
ASP underdrive pulley system

Professional assembly & engine installation

Lingenfelter high flow air intake system

All necessary gaskets, fluids & bolts
Professional assembly & engine installation
Engine testing & expert ECM tuning
Chassis dyno testing before & after installation
Lingenfelter 2 year / 24,000 mile warranty
366 CID LS2 490 HP Package Price

Price - $7,695.00
*Includes automatic transmission shift improvements. Some applications may benefit from a higher stall torque converter. Please ask your salesperson for details and prices. Normal installation time required: 2 weeks with prior notification. Items on this page are not legal for sale or use on California pollution controlled motor vehicles unless they are listed with an E.O. number

you should see their packages for bore out to 427