That's not a pic of your engine right? The air cleaner is black. It's kind of hard to tell in that picture if it's natural or plated. Zinc plating back in the 70's didn't look very bright compared to zinc plating today. Looking at the throttle cable clamp and the bracket from the pivot to the carb...they look to be close to the same finish. Both of those pieces were zinc plated I believe. I guess if they've been cleaned, the original finish could have been lost.
The yellow paint on the kickdown linkage is interesting.