You would be better off putting 32 Plymouth question as the title of the tread.
I think you are looking for the running board apron or sometimes splash aprons,. The run from fender to fender and below the body to the running boards.
There is several different blacks. The 9300 has a slight gray hue to it, blue black, jet black are again slightly different.
DuPont and Ditzler when mixed ends up looking like semi gloss paint. (SNAFU)