There is no magnum manifold that is as large as the 340. That's the reason that I started machining the magnum manifolds, to make them as large as the 340 manifolds. The XXX18 passenger will have a hole (like the XXX19 driver) that is close to the 340 (2 1/8"). But the XXX18 was not one year only, it was used in 92 and 93. Also the XXX18 passenger manifold exits close to the fire wall in an A body, they will work but they transfer more heat to the passenger floorboard.
