What tach is this?

Both applications have a very similar look and may be the same exact tach assembly. The electronic box is the sending unit for the tach. If this is an "A" body tach it is a '64-'65 only. '66's used an integrated tach inside the guage cluster.

No A-body tach in 1964. Check out this thread. It looks like the '65 Formula S may have used the same tach as the '64-65 B-body. [FOR SALE] - 1965 Barracuda Formula S Tach Unit