[MultiMopars]

Yes, factory mistakes happened. The line never stopped, if the bin for the required item was empty they put in what would work. It was expected that the DEALER would catch the mistake (which MOST were) and have it corrected under a warranty claim.

BTW, the 1965 Corvette 395 h.p. cars were factory available with A/C and they had a 6500 tach in them.

I think that in MOST cases you can rely on what the ORIGINAL FACTORY tach shows in a car to help determine what engine was in it. Anyone can look for faults or exception to the rule to discount or prove a cars true heritage.

The bottom line is that in these cases unless you have some other factory paperwork to support your claims it all comes down to what the guy writing the check when BUYING one of these cars believes.