The housings are the same, regardless of ratio. The carriers are different. The ring gear bolts to the carrier.
Salmon is right: The carriers are identified by their casting numbers. The carriers are specific to a range of gear ratios. 3.36 is the break point. Below 3.36 a "2-series" carrier is required. For 3.36 and above, a "3-series" carrier is required.
You can use a "3-series" posi or non-posi carrier with the same gear set, in any housing.
I do not have the casting numbers handy for the Firebird 10-bolt carriers, and I do not know if they are different than the "A" body carriers, of which I have one of each.
