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This is the latest version of the LT4, you can tell by the taller intercooler/supercharger top which is thicker and is straight across. The earlier version was thinner up front and kicked up slightly in the rear. After the first version came out there were issues with overheating on tracked Z06 cars that went into limp mode. To solve this issue GM designed larger intercooler bricks that necessitated a thicker cover for the supercharger.