Ok so I have been doing A LOT of searching on line this afternoon looking at hundreds of pics of how they detailed 8 3/4 rear ends. I have seen all black(which I do not believe was correct) to 3rd members being black to cast. Backing plates black to cast. Leaf springs black to cast. Hangers and u bolts and shackles all cast to black. So what truly was the way they did it? Any pics?

Dave Waldens white -70 Challenger is a good reference.

http://www.moparaction.com/Article/PoP/PoP.html

I carefully dis-assembled, photographed, and documented my one owner 1969 A body 8-3/4 rear end, and this is what I found:

3rd member - bare cast iron, as cast color with lumber crayon marks and paint daubs. No spray paint at all.

Housing - looks semi gloss black, but a lot of people say it was originally a cheap gloss black that faded. Most people agree SG black is the "right" look. I saw black paint overspray droplets inside my housing.

Brake backing plates - most definitely dark gray phosphated (Parkerized), not any kind of paint at all.

Leaf springs - as heat treated color. There are paint daubs over bare metal on the forward end which proves mine had no dip or spray paint. I plan to duplicate the heat treated color by experimenting with gun blueing. There have been several threads here about gun blueing springs.

Hangers, U-bolts/nuts, shock plate, shackles - all bare metal on my car. I believe there is very wide agreement on bare metal. HOWEVER, bare metal does not always mean silvery. Hangers and shackles were stamped from hot rolled steel sheet; shock plates were stamped from hot rolled steel plate; both likely had dark gray mill scale on the top and bottom surfaces but not on the sheared edges. Look at new bare metal U-bolts and nuts in a hardware or parts store, and they are dark colored, not silvery. You can attain a dark color on chemically de-rusted bare metal by wetting with 2 coats of phosphoric acid a week apart and wiping off the second coat. I like Rust Cure (phosphoric acid) for this. Do NOT soak any part in phosphoric acid for very long due to very pronounced acid etching.

This is the best photo I can find to show that the brake backing plates are phosphated, a dark gray to almost black look, usually dark gray. Phosphating (Parkerizing) is the same process as the gun metal finish on military firearms. Parkerizing is a gun smithing process that's fairly easy to DIY.

This photo is the outboard side under the drum before cleanup. After they were cleaned up, it was even more evident that they were phosphated.