OK thanks, looks like you have a matched set there, they probably came stock on the 273 Commando 4 bbl.
Being you have the bell fittings for the exhaust pipe instead of the flat flange tells me what you have there.
That last picture I Put up on the 340 manifolds were like 1973 version, so that is one reason the passenger side looks different than yours.
It's all good, just wanted to understand what you have going there.
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My friend's 72 Duster with a '69 Stock Built 318, 9.2:1 compression , newer 302 closed chamber heads and a 340 cam. All mopar parts on the build including the LD4B intake manifold. Has the Edelbrock 1406 4bbl carb.
That big exhaust system is one of the major parts of the build that makes it really perform, with the cast manifolds on too.
Goes like a son of a gun, need to keep both hands on the wheel when you put your foot into it. It Goes . . .
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