I can tell you that Chrysler Power item has a lot of items that don't match Galen's numbers, and I would side with Galen on this.

Additionally, for whatever info I've collected over the years, it seems that 1971 color numbers are not as complete as 1970's. Years ago, a guy in Ohio (owned the two-tone V-code '71) showed me a Galen printout with general Barracuda numbers without specifics by model/trim level. But then, a number of years ago, someone on this site (Alan Gallant?) had something that narrowed that info down (for only a few colors). Alan's list doesn't have GK6 by model, but it shows that 977 US-spec Barracudas (all three models) built in that color.

That's rarer than I had expected.