brass washers for manifold

Kickdown lever or kickdown rod. See this article. It is actually a post from slantsix.org about converting from a one barrel to a two barrel. The linkages for the one barrels are different than the super six linkages. What carburetor does your 71 Dart have?

Here is how the linkages attach to the carb:


You must also adjust the kickdown linkage once it is installed:



You can actually damage your transmission without the kickdown installed.