If memory serves, you have the 8.25 inch ring gear. With one exception (Oldsmobile), the term 10 bolt and 12 bolt rear ends actually referred to the number of bolts securing the ring gear to the differential and not the number of bolts holding the cover to the housing, though with the exception of 1970 and earlier Oldsmobile A-bodied cars (Cutlass/442), the cover bolts happened to match the number of bolts of the ring gear. The Olds had 12 bolt covers on a 10 bolt rear. Your F-body Camaro/Firebird came with a 10 bolt rear end.
As a side note, the sleeper builders would adapt a 12 bolt differential into a 10 bolt housing to fool the other racers into thinking all you had was a weak little 10 bolt rear. Significant machining was required to stuff a 12 bolt differential and gear set into the 10 bolt housing, but the idea was to lure the other racer into the bet.
