What color were the 489 diff cases painted from the factory. It is going into a '72 Cuda. Wasn't sure if he were black or if a cast blast would be more appropriate.

Also, what color should I paint the yoke?

None of those parts were painted from the factory. But, the case was natural cast iron, the yoke dust cover is usually yellow zinc and the pinion yoke is natural steel. All of these things could be mimicked with paint obviously.

I've been using Duplicolor cast iron high temp paint on parts like this. Of course my cars are no where near the quality of the guys on here, but I try.

who have tried Daves' RPM?
seems like the best way to preserve raw steel,cast iron and aluminum.

I soaked my diff case in Evaporust and then washed it off with acetone. I added paint daubs and then applied RPM. The diff is in my garage and won't be under my car for some time. For what it's worth, It looks like the day I did it but it hasn't seen any exposure to the elements.