Remflex Exhaust Header Gasket GM CHEV OHV 348 / 5.7L 409 / 6.7L # REM2020Remflex Exhaust Header Gasket GM CHEV OHV 348 5. 7L 409 6. 7L # REM2020 GM V8, OHV, 348 5. 7L ('58 '61), 409 6. 7L ('61 '65), 1 5 8"w x 1 7 16"h Square Center Ports, 1 7 8"w x 1 1 2"h Port Style: Square port Gasket Material: Graphite Quantity: Sold as a pair. Notes: Center ports are 1 5 8 in. wide x 1 7 16 in. high. End ports are 1 7 8 in. wide x 1 1 2 in. high. Suggested torque of 20 lbs. ft. Remflex exhaust header gasket sets feature 100 percent