.....would the running board-to-bed filler panel be black or silver? What about the front splash apron or the rear bumper filler panel?
These are all a matter of personal choice.
..... originally, the board-to-bed filler was bed color (however, anything was possible on a special order paint job)
..... originally, the front splash apron was the exterior body color (however, anything was possible on a special order paint job)
..... originally, there was no rear bumper filler. However, the bed color might be a good choice.