'68 Barra CARPET

José,
Hello back.
The '67-69 Barracuda had two pieces composing the floor-pan carpet, front and back pieces.
In the Chrysler Parts No. Book for 1968, the front piece carries the same no. for Coup(23), Convertible(27) and Fastback (29), part no. 1789CX8.
The rear piece is represented by two different nos.: 1777CX8 for coupe and convertible; and 1710CX8 for fastback(29).

That being established, nowadays the offering comes a few parts suppliers like Year One and Legendary Auto Interior (product is identical).
These carpets are not differentiated beteween coupe of convertible Barracuda; they are represented by "1967-1976 A-Body group" as the carpet cut is made ubiquitous, fits-all piece of trimming. The difference made is for Fastbacks which are delivered with 9 pieces of trimming.

The body shop guy who installed the carpet in my 4-door Dodge Dart (3'' longer wheelbase) had to spare some pieces from the old carpet to complete the trimming on the side of the rear seat. This goes to exemplify how ubiquitous the offering under ''1967-1976 A-Body !!" really is.

In conclusion to this, my experience is that, yes, you could buy the carpet I have from Legedary that applies for A-Body 1967-1976 (no console, automatic shifter on the steering column) for your fastback. You would have to do some trimming to complete the furbishings onto the sides of the rear seat from pieces you'd spare from the old one or from the overlap.
I am going to put this letter in the forum so that you can collect other view-points.