As far as lights, I have found the best prices at FBI. You can go to sites like truckperformance.com for filter kits, etc. If you are looking for internal engine components, good luck. The L29 Vortec 454 has a serious lack of internal components available. You can get the typical headers, mass air flow, throttle body spacer, underdrive pulleys, etc.
http://www.truckperformance.com
http://www.stylinconcepts.com
http://www.fbimini.com