['ol Pinion head]

When get a chance in a week or two will take a closer look at the June '70 stamped COZ T/A rear I have in one of my housing racks. Have had that very clean core rear for many years. Of the more common application '70 F-body usage 12 bolt rears, have had quite a few clean ones, but most were just COS & COT coded 3.07's. Most I've built them up with aftermarket gears, new axles, & rebuilt Eaton posi carriers. One COS coded 12 bolt I have, decades ago i strapped it under the front of the frame of a '70 GTO body on frame. had no upper & lower control arms & disc setup removed. Made for a quick way to make the partial project a roller. After several years setting outside on the concrete, i removed that particular 12 bolt from under the front frane. The axle tubes & housing were just surface rusty, if it had any black paint on it, it was super thin to begin with.

On McKinnon mfg original Olds, Buick, & Pontiac usage 12 bolts, I've confirmed both factory painted & unpainted original housings. McKinnon did quite a few things differently on the 12 bolts they built for non Chevy usage, i.e, in our interest, '70-72 Pontiac A/G usage. Differently, as in not just different coded housings, but different style backing plates, different drums, different factory axles, & of course a 3R pinion flange to directly bolt up. Last there were no silly color band stickers wrapoed around the the axle tubes to quickly ID the ratio of rearend at the assembly plant. Instead, a two letter code was painted with a stencil at the McKinnon plant on the face of the drivers side installed brake drum. Am not sure it's wise to categorize the McKinnon 12 bolt built rears in with the much more common 12 bolt c-clip axle rears being built out of, say, the Bufflalo axle plant.