Caddyman, the LS 1 and it's derivative, the LS 6 that was used in the C5 Corvettes and the 1st gen. CTS-V shares little, if anything other than pushrods, with the old Chevy smallblock. It is a clean-sheet, aluminum block engine that was introduced in the '97 Corvette. It is cast in iron only for trucks. The current CTS-V has a supercharged 6.2 liter version (LS 9?) with 550+ HP.
I can't vouch either way for the Northstar's reliability, as I've never discussed it with anyone who has owned one, but those bad boys sure run when they are working! I think the Northstar was derived from the Lotus-designed LT-5 that was in the ZR 1 Corvette from the late'80s/early '90s.