You've reversed yourself on this over the past decade or so, and your statement including 1968 led me through the looking glass. Damn you! :p
Several hours of digging and cross-referencing later, this is what I've found, along with my thoughts--not absolute statements--about it:
Good design dictates that the orientation of the tachometer numerals (radial v. horizontal) should match those on the speedometer. 1967 was part number 2771656, radial numerals with 0 at the 8 o'clock position (standard sweep). 1969-'71 used part number 2857729, which has level or upright numerals and the sidewinder sweep (0 at 5 o'clock) in its service-part incarnation. This version is what's listed in the final 1968 catalog as well.
Service parts are not always the same as assembly-line though, and the parts books aren't gospel either, because they got revised multiple times. Chrysler would send new pages and tell the dealer to toss the old ones, which without fail the latter did. I've never seen a complete first-printing Mopar parts catalog prior to 1994--because I was there when that one dropped.
So, bearing that in mind, let's get confused:
1968 is a bit of a trick. It's possible there's a 1968 radial-numeral, side sweep production tach but I don't recall ever seeing one nor can I find evidence of one. It's also plausible and quite possible that some (or all) '68s were actually built with the '67-style tach, since 2857729 is shown as a "changed or added" number in the final revision of the '68 catalog. Without fail, that means prior printings of that catalog listed a different part number. That revision didn't appear until March of 1969, most of the way through the following model year. They probably superseded 2771656 to the current production tach (2857729) at that time.
Bear with me here: The 1968 Rallye dash speedometer used radially-configured numerals, same as '67. The final revision of the 1967 parts book was printed in January of 1968, long after the '67s were gone--but only halfway through the '68 production run. They had not yet changed the Rallye speedometer to the upright numerals yet at that time, so it makes sense that 2771656 appears because it was still in production use on the '68 models. Then, most of the way through '69, Chrysler decided they'd only service one tach--the current 1969 production unit that matched the upright speedometer numerals used 1969-'71--and superseded it in the final revision of the '68 catalog.
I find this scenario not only plausible, but quite probable. Why suddenly switch to a mismatched tach for no reason? The scale was still 6,000RPM/270° sweep, and I'd wager the internals are identical--they just rotated the needle and changed the face printing. It's likely they put the "in-production" tach part number in the catalog at the time of printing. By the final revision of the 1968 catalog (3/69), that would be 2857729. They were all done revising earlier catalogs, so when someone ordered the earlier tach part number in the '67 book, they'd simply get the late one. Fit and function are the same, it just looked different. At no time in history did Chrysler care about "correct" or that an idiot like myself would be worried about anything so silly 50+ years in the future.
The only way to truly know would be to find first-/early-edition 1968 catalog pages. Mopar parts department protocol being what it was, good luck. When the next printing came out, the old pages got tossed. I did a bit of that myself, luckily much later. However, people restoring first-year Neons are gonna eventually hate me.
1967 Mopar catalog, V8 part number and catalog revision date highlighted:
View attachment 1716043456
1968 Mopar catalog, V8 part number, catalog revision date and * footnote highlighted:
View attachment 1716043457
Look at the "Supersedes" dates on both pages, then consider that they had to have a working parts catalog when the new cars appeared on September 1st. By March or April, the catalog was probably on its third or fourth revision in less than a year. It got another, final revision more than half a year later.
Just for fun, I entered 2771656 into the current Chrysler parts system. Wouldja lookit that:
View attachment 1716043463
Unfortunately, the system doesn't provide supersession dates. Still, I would bet that one was almost 54 years ago.
Those of us with Rallye-dash E-bodies are familiar with this situation, as the part number never changed (that I can find) on the E-body tach, but 1970-early '72 used an 8,000RPM scale, and everything after that used a 7K scale. From 1972 forward, ordering number 2984185 could get you either tach. The same situation existed with '70-'71 Rallye wheel centers. Then again, the final revision of the 1970-'71 book was printed in January of '72. Was the number superseded in an earlier revision? I'd pay good money to be able to see an original 1970-only version of the Mopar parts catalog. It existed once.
With all of that in mind, if I owned a 1968 Barracuda I would definitely install the 1967-style tachometer. The 1969 version would clash badly with the speedometer, a mistake I don't think Chrysler would've made. If anyone has a 1967 or 1968 factory-tachometer-equipped Barracuda that they personally bought new, I'd like to hear their input.
One really can't speak in absolutes about these old cars when the company that built them was actively destroying paper trails multiple times yearly. One thing that is sure: There is no existing record of an A-body sidewinder-scale, upright-numeral tach prior to March of 1969, and the only tach listed for 1967 has a standard "8-to-4" scale and radial numerals.
Also, my '74 E-body has an 8K tach, what-fer I like it gooder. So nyah. :poke:
