I really like the Thule 421 Xsporter truck rack as a superb solution for carrying a kayak in the truckbed of your 2000 Chevy Silverado. You can then attach the Thule 883 Glide-and-Set kayak rack (or something similar) directly to the Thule 421 Xsporter front and rear crossbars for hauling your kayak. Also as a side note if you ever wanted to use the truck rack to carry a canoe or lumber, ladder etc you are set to go because the Thule 421 Xsporter comes with a set of Xstops that you can use for carrying these items. You might also want to visit this
list of chevy racks photos or this
page of chevy truck rack pictures for an example of this kayak truckbed rack system installed on a Chevy Silverado.