I won’t even attempt.
Easy to tell when you pull the rear cover as the ring gear bolts are different size and thread. I can’t remember sizes off hand, but easy enough to look up. I have an 8.5 that all the experts claimed was an 8.2 but easy to miss visually from looking at the outside. I pulled out of a ‘72 Cutlass. I’m sure Ol Pinion Head might be able to tell.
__________________
‘63 LeMans- ‘69 400 w/ original transaxle. 2.69 gears.
‘55 Catalina
‘62 Mercury Meteor-all original, bought new by my grandfather
71' GTO -original 400/4-speed/3.23 posi
13.95 @ 102.1 on street tires @ 4055lbs.-now my sons ride