Try Fel-Pro's quality high-performance gaskets.
Most Fel-Pro Performance intake-manifold gaskets have Printoseal construction, which puts beads of special elastomers around the ports for extra sealing power. They also feature a non-metallic, rubber-fiber base material that resists gasoline and alcohol, while allowing engine builders to precision-trim around the intake ports.

Gaskets, Manifold, Intake, Composite, Rectangle, 1.82 in. x 2.54 in. Port, .060 in. Thick, Chevy, 396-454, Set