Leitner no longer claims to have fitment for their racks on 1st Generation Chevrolet Silverado 1500 trucks. But I measured and measured, and it seemed to me that the racks for the current Silverados would fit. I contacted the guys at Truck Brigade and they said according to their measurements, it should fit. So I pulled the trigger and bought the rack. As you can see in the picture below, it fits. Thanks to Truck Brigade for taking the time to check my measurements, and Chevy for keeping the bed size stable. This is a standard box (6.5 ft.), Extended Cab 2006 Silverado. The rack I ordered: Leitner Designs Active Cargo System – Chevy Silverado 1500 (2007-2020) 6′ 6″ Bed.