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I don't know what the current GMPP part number is for the Z/28 pan, but it was P/N 360450 when it was also used for 1975-79 L-82 Corvettes (with the thick front seal). The Z/28-L-82 windage tray that mates with the rails welded to the sides of the oil pan is still available as P/N 3927136, and the main studs are P/N 14087508 (originally P/N 3960312). Photo below is the windage tray (baffle).