Welp during this mornings eyesight check John (him or me) I don't see any exhaust gasket in the parts illustration, I hope he isn't confusing #58 which is the intake manifold gasket.
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Now the fun part of deciphering parts manual numbers, #58 just mentions gasket but a reference to 9-50-1,
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onward to text page 9-16, 9-50-1 engine column shows GASKET SET, Intake Manifold (correct)
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but if we scroll down we see that there if a 9-50-5 GASKET, Exhaust Manifold Left, in the 318 (column)
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but notice the car line of V, L which stands for (scroll to bottom of page) the Valiant & Dart line. I don't know what the w/Heat stands for, Heat Riser? Interior Heat?
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So it seems to be there is a factory exhaust gasket that is not shown in any illustration's that I can find but for only the left side for some reason and on two car lines. V8 in the small car line with a smaller engine compartment means more heat? Of course this I'm sure can vary by year.
Only MA Mopar will know (or any super duper parts guy).
Your choice if you want to use gaskets, back in the old daze I never saw gaskets on the cast iron manifolds (Hemi has them, but a very rare sighting for me) only saw gaskets on headers and if I see them on the cast iron manifolds my brain thinks somethings wrong.
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