Maintaining consistent internal pressure and preventing leaks in your engine is made easy with our selection of 2004.5-2005 GM 6.6L Duramax LML Gaskets! Here at Alligator Performance, we offer an excellent variety of high-quality gaskets and gasket sets that range from basic stock replacements to complete performance upgrades. Our gaskets are curated from trusted manufacturers so you can outfit your Sierra/Silverado 2500HD/3500HD with high-quality upgrades. Check out our full lineup of Engine Upgrades! GM Duramax Fitments: 2004, 2005 GM 6.6L Duramax.Submodel Fitments: WT, Custom, LT, LTZ, High Country, 1LT, 2LT, Pro, SLE, SLT, AT4, Denali.Some exceptions apply, please see individual product pages for specific fitments.