I wanted to go down this route but junkyard posi's were not available. I decided I wanted the Eaton Posi for the 8.2 BOP instead. I was going to buy new axles, master axle kit, and gears. It was going to cost about $1200. I decided to go a different route. I found a Corporate 8.5 10 bolt rearend out of a 1973 Pontiac Ventura (Nova clone) $150. I bought new Richmond gears off Ebay for $100 shipped, new Eaton posi off Ebay $300 shipped, new high strength axles $200, master kit $90. So for about $300 dollars less I was able to get a stronger rear-end. I scrounged the junkyard for a posi and gears but they had all been picked through. If you could get all the parts from the junkyard you could potential spend around $400 for everything except axles. You could rebuild the posi for another $80.
The reason I went with the Nova rear over a 2nd gen Camaro is the Nova rear is about 1" narrower than the Firebirds rear but the spring perches are in the exact same place. Here is a good article:
