ORIGINAL: 66Cuda
I still don't think that is a 67, in 67 it was still more of a fastback look, the back window went back a lot farther. in 69 they moved away from the fast back look and the deck lid increased in size.
I'd almost guarantee that is a 69. I'm at work so I can't look it up though.
Lack of side markers would indicate '67. Plymouth Barracudas shared body style in years 1967 through 1969. This example is just the notchback version... not the fastback. Fastback and notchback versions were available all three model years. Major body change to e-body in 1970 marked the begining of the short deck.