Unique speedo cable?

Keith Mopar said
I did change out a speedo cable on a 66 Barracuda with a 67 model cable. I found the 66 Cable was close to 4" shorter than the 67 cable. I purchased a new replacement cable from National Moparts for a 67 as 66 was not in stock and that replacement cable was very close to the length of my original 67 cable. The ends were correct and so was the grommet they supplied.
I figured the length difference was due to early A to later. I didn't realize they should be the same part number.
I garbaged the original cable so I have no part numbers.

The factory parts manual shows a different part number between a '66 and a '67, but, some parts suppliers list them together. It's just weird that an NOS Mopar cable with the correct part number for '66, is the wrong cable. The '66 parts manual shows this cable as being the same for all '66 cars, as long as they don't have auto pilot. That struck me as strange too, as I figured B and C body cars would use a longer one than an A-body.