It´s another story but I had a 1967 Impala with a 275 hp 327 that was built in Canada. It was supposed to have a 10-bolt rearend with a 3.08 posi in it. It actually had a 12-bolt with a 3.07 posi in it, and it was date-correct for the car. I´m thinking it was a glitch at the factory that made this happen. Maybe they ran out of 10-bolts and installed the standard Taxi-car 12-bolt instead ? We will never know.
