For 2001-2003 Chevrolet Silverado 1500 HD - with RPO Code GT4; with RPO Code GT5. For 2005-2006 Chevrolet Silverado 1500 HD - with RPO Code GT4; with RPO Code GT5. For 2007-2007 Chevrolet Silverado 1500 HD Classic - with RPO Code GT4; with RPO Code GT5.
