67 BARRACUDA CARGO CARPET

I wonder if no fold down rear seat was standard to keep the advertised base price of the 'Cuda model low.

Also, were bucket seats standard on a 69 Formula S fastback? I thought there were some unique standard interior items to the 69 'Cuda model?

Just like in 1970, they made the standard transmission in a 340 Swinger a 3-speed. Keeps the advertised base price down.
There was a definite trend towards "de-contenting" the 69s for price competitiveness, especially considering they hadn't hit their sales targets either of the previous 2 years. I don't think bucket seats were ever "standard" except in convertibles. Seats were never a part of the Formula S package AFAIK.