I can't comment on how the Chevy rag joint looks, but the NOS part available for the '70 Olds has a few subtle nuances from the assembly line piece. The splines on the factory clamp go around maybe 45% of the hole, whereas the NOS #7828871 has splines around the entire hole of the clamp. The original rag joint (coupler) also has the letter 'F' stamped in to the tall end of the "pin" (or whatever the permanent fixture is called on these things).

I sent my hardware out to be phosphated, and I'm looking for a source that will copper plate one of the original bolts. There is an awesome article on one of the Chevelle sites that breaks down the reason for the copper plating and how it impacts the ability to torque. I'll see if I can find the link and paste it in this thread.

A chrome shop should be able to copper plate the bolt. I'm pretty sure that chrome parts get copper plated before the chrome goes on.

Correct, triple plating is the most expensive and durable process, which involves plating the steel first with copper and then nickel before the chromium plating is applied.

Doing one of these on my 1970 Camaro now. Is it for sure that the 5/16-24 thread bolt is copper plated on the 1970's? From my research, there was a changes occurring in this component from 1969 to 1970. The separate wire connector went away. Hard to find info on this. Does anyone have a correctly restored or low mileage assembly line (not NOS...they are different I've found) coupling?