The 72-73 340 manifolds will work just fine, but make sure the drivers side is for an A body. Passenger side is the same between A, B and E bodies, but the drivers side is specific for A body cars. The only difference between a 68-70 drivers side 340 HP manifold and a 72-76 340/360 drivers side manifold is the later ones have bolt bosses cast in to hold the heat stove that the heat tube going up to the air cleaner hooks to.
