Your 1999 to 2006 Silverado or Sierra will look great with a new set of headlights and tail lights. On the Silverado side there is a difference in the 1999 to 2002 models from the 2003 to 2006 front end upgrade. But for the GMC they are the same right from 1999 to 2006. The only difference in the park lights on the Denail and C3 models is different. The Tahoe and Suburban use the 1999 to 2002 stlye headlights right through from 2000 to 2006. The rear lighting on the trucks is the same on all except the 2003 to 2006 Silverado on which they added a separate marker light on the tail light. The Tahoe, Yukon and Suburban use different tail lights than the trucks do for this body style.