Looking for any documentation '69 Barracuda Fastback

I thought the by 69 the "489" diff case was on production? My 67 S has 741, my 69 S has 489.
Could have simply been swapped once(or twice) in the last 50 years.
Very cool car.
Fendertag pics?

Sadly, there is no fender tag or build sheet, which is why I'm trying to find out any info I can by checking for clues.
Thank you much for the help.