i had a body shop from 1973 to 1976 and vinyl tops were very popular then. ALL of the manufacturers offered vinyl top options on almost every model line. AND it was very common for repair shops to install "custom" vinyl tops on pretty much any car a customer wanted a vinyl top on. i have no doubt that an early owner of your car decided to have the top noted in the other car pic you've posted put on. i agree with you on the floral top/slick back issue - the sales literature that i have for 1969 Barracudas only show the "floral" tops on the Barracuda coupe. however, i am pretty confident that there were more floral top coupes ("Mod Top" option) ordered than there were "slick back" vinyl top fastbacks. i could be wrong, but i have never seen a real slick back fastback other than in pictures on the internet.