http://www.mar-k.com/_assets/images/instructions/2007finalwoodtest.pdfAs you pointed out, all finishes failed. except for the exterior house paint over POR.
http://www.mar-k.com/_assets/images/instructions/2010woodtestupdate.pdfOtherwise, as much as possible, keep the truck/bed out of the rain, snow, and sun.
It will be interesting to see if anyone posts more recent tests than Mar-K's.
I want my '54's bed wood to look original - semi-dull black.
I will try a mixture coal oil and stove black - reapplied regularly until I am gone.
Jim Carter's article on bed wood finish.It is understandable that you might might to show the color/grain of better/different wood.