Correct 12 bolt pinion flange for LS-6 rearend ?

[SS427]

9210 is correct for the 454 flanges, I do not have the numbers in front of me for the 396 cars. Oddly enough I have come across several original unrestored low mileage LS-6 cars with the CCF 3:31 rears installed in them as well as the 9210 flange but the build sheet did not call out for that rear as it should have been CRV. These rears are also date coded correctly for the cars. As of yet I have no explanation for this but have seen enough of them to make me wonder.

In order to put a CCF rear with a 9210 flange into a 396 car they would also have had to change out the driveshaft as the 396 shafts are also different then a 454 shaft. I will assume your friends car has a Turbo 400 or they swapped in an M-22. Attached is a picture of the 9210 flange.