Will a 340 exh. manif. 3614368-2 made for std trans work with a 904 auto

That listing is wrong. That number is a 72+ Drivers side manifold.

68-71 340 drivers exh manifold is 2863553.

Those numbers and verifications are from the parts books for 70-72.

That said, the manifold will work on a 70 Dart

There is no designation for auto or 4 speed. They all used the same manifold for each specific year.