An LA manifold sits across a big span of alloy and iron that expand at different rates, so the gasket has to seal without needing a lot of clamp load. Cellulose nitrile does that, and because it cuts cleanly you can open the ports up to match a head that has already been worked.

Mr. Gasket 307G Performance Intake Manifold Gaskets Features:

• Fits 1967-1972 Chrysler 318, 340 and 360 LA Small Block engines.
• Rectangle ports measuring 1.17 in. x 2.27 in.
• 0.060 in. thick.
• Manufactured from cellulose and nitrile composition gasket material.
• Can be trimmed if necessary for modified port applications.
• Complete with manifold end seals and distributor gasket where applicable.
• For original equipment replacement, high performance street, drag race and oval track use.