On that intake manifold hot exhaust gas from the heat crossover comes up in that channel to heat up the carb for better cold weather driveability.
A felpro 60043 thin paper gasket and then a 60731 stainless steel heat shield and then techinspector's 1/4 fiber spacer is required.
Without the stainless heat shield hot exhaust gas will burn up the 1/4 fiber spacer.
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