Mr Gasket 5921 Ultra-Seal Exhaust / Header Gaskets Application: 1963-1979 Pontiac 326-455 V8Oval / D Ports 1.55 x 2.00 inchFeatures: Has A Steel Core With Graphite Facing.Graphite Facing Has Excellent Thermo-conductivity.High Recovery Mat Allows For Better Seal Retention.Can Be Trimmed For Port Modifications.Expanded Steel Core For Stability.These Gaskets Have Slotted End Holes.