Can anyone tell me if there is a reason Chevrolet dropped the heater box floor dump duct in the 1968 Camaro? The 1967 AIM shows this as item 5 #3895933, UPC 1/A7 and item 16 #3889486, UPC C60/A6. The 1968 AIM dropped UPC/A1 and does not show the duct on UPC C60/A6. The 1968 AIM does however reference the duct on UPC C60/E4 with no part number. I am trying to decide if this is correct for my 1968 Camaro with factory air conditioning.