Doug's Headers D314-R Exhaust Header for Chevy C10 LS1/LS6 Swap 1973-1987 C10 Truck LS1-LS6 Swap 1-7/8'' Tube Diameter 3'' Collector SAP Port Shape 3/8" Thick machined flanges...no warping; CNC mandrel bent tubes... accurate fit & better flow; Precision formed long transition collectors and long tube design... reduces backpressure and increases higher RPM horsepower; Heavy 16 gauge tubing...longer life; Tubes are pre-polished to remove scratches and the header is left unfinished (raw steel) for individual customizing