2003 GMC W4500 Forward Engine: 6.0L V8; Oval Port; Beaded Steel;. 2004 GMC W4500 Forward Engine: 6.0L V8; Oval Port; Beaded Steel;. 2005 GMC W4500 Forward Engine: 6.0L V8; Oval Port; Beaded Steel;. 2006 GMC W4500 Forward Engine: 6.0L V8; Oval Port; Beaded Steel;.