340/360 Drivers Exhaust Manifold ID?

Howdy peoples! I have a 68 340 motor that came with only the drivers side manifold. I’m trying to identify it, but the casting number doesn’t show up in my books. A fine young gun is looking for a drivers side manifold for his 69 Dart project, he’s putting in a 5.9 magnum, and I told him I would try to check the application on this one before I sent it to him. The casting number is 3870337-1, which I thought looked like a truck manifold. Anybody know what the application is for this?

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