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The way i see it is it came with a gasket it should have one when it goes back together, so either the proper gasket or a thin bead of tubed gasket
DO NOT use any kind of sealer, or tubed gasket, on it. Put a NEW gasket on it when it goes back together. It cost less then 5 bucks, don't go cheap on that. It'll only cause problems in the future if ya do.