I had some pretty bad pitting on the chrome trim pieces when I installed the folddown seat on my 68. These pieces were (are?) not available, so rechroming was my only option. They turned out better than I had hoped.
I am not speaking from experience but here goes.
i suspect that as long as the piece is still recognizable then it can be rechromed. the quality of the job is just like painting. The quality is in the preparation. All the pits add to prep costs.
The pits can be filled with copper. the copper part of the process is primarily the filler. The nickel and chrome follows. This is the triple plate, sometimes referred to as "show chrome".
Pot metal pieces are the most susceptable to pitting. There is a product called solder it by caswell. this is for filling pits in pot metal prior to chroming. In fact if you vistit the caswell site they sell kits for just about any task.
They say pot metal is very dificult to get right. These kits also do not provide instant excellent results. It takes practice.
I have been thinking of using something like this.