There was also a BOP 12-bolt, which was essentially a 10-bolt with a 12-bolt cover. This was the rear end that made it into the BOP heavy duty applications in 70-72. It uses bolt in axles, not c-clips, and the cover has a different shape. This is what's under my 69 Firebird.
Rob, thanks for the

I really have to make the trip to see these Pure Stocks in person. BTW, they just released those coveted RAII/RAIV exhaust manifolds for the 67-69 Firebirds, and believe it or not, they have a version with a 3" collector! I was seriously thinking of going back to RAIV heads and using these manifolds to see what would happen, but I realize some of the really serious "stock" guys have a lot more serious internal engine mods than I care to perform right now. I still have a hydraulic cam, cast rods, and big ol' TRW slugs.