I don't know what you had without a picture, but the manifold in question above is a factory unmodified piece. "I THINK" the 68 340 had symmetrical venturi and the 69 and 70 had the larger secondaries, then the 71-73 had the TQ. I do know "there was" a 340 intake where all the holes in the pad were the same, I am just not sure which one it was.
