Rick's First Generation Camaro has them used for sale, I think they all are rebuilt before sold. They have 12 bolt units with either drum or disc brakes. I see you are in Pinehurst, NC. That would only be a short trip to Athens, Ga to pick one up. That would save alot on shipping.
'69 SS 396/375hp L78 M21 3.73 Fathom green/medium green interior
Last time I called Ricks about a 12 bolt they only had one and it was a 4:11. Yes, it was rebuilt and completly ready to go $1,200.00. For some reason I thought they would have a bunch to choose from. Not the case. Maybe they sell that quick.
why not just build up the 10 bolt they can- be built to hold up under some very serious hp. i have a friend who runs a 10 bolt in his drag car, the car goes 6.30s in the 1/8 on the bottle. moser sells some good parts for the 10 bolt, and i think it will be alot cheaper than buying a brand new 12 bolt.