8.5's will take a 3/4" wrench on the ring gear bolts, not 11/16.
Another way to tell is the bolt that holds the spider gear pin in. If it takes a 5/16" wrench to remove, it's an 8.5. If its an 8.2, a 1/2" wrench will be the ticket.
I'm gonna agree with DZAUTO that it is almost positively an 8.2.
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70 & 1/2 RS Camaro
SB406 & M20 4spd
9" Rear
70 Malibu
SB350 & TH400
Gold Member # 103
Driveline Technician