Funton,
I am currently in the process of re-finishing the bedwood in my "56 3100. I read the Mar-K study on different bed finishes, and opted for BLACK wood, but, with a change from what Mar-K did. I am applying 3 coats of Glidden "Gripper" exterior primer (grey color) instead of the POR-15. (Have you checked the price of POR-15?) The three coats are being put on, with a minimum of 2 hours between coats, and I use a 7" nap roller to apply. When I get finished applying the primer, I am going to apply 3 coats of Behr's exterior gloss black, giving a minimum of 6 hours between coats. I feel the primer I chose and the Behr's will give the protection I want for the bed (I only haul AIR in the bed of my truck!). Lots of luck with whatever you chose.
Brian