I did it to my '93 ranger, I paid a little extra and had rhinoliner do a medium grey, similar to the seat color. I also had them do over the top of the rains and the tailgate about 2 inches or so. It was enough to get fully around the stake pockets. Can't tell you how many times I was very glad I'd done that - I've hauled countless tons of rock, dirt, and landscaping stone without issue.
In my experience with Rhinoliner it did fade a little, but being grey not a big deal. It saved a huge amount of wear and tear on the truck. I did have rust underneath the lip of the tailgate at the seam at the bottom, but that would have occurred anyway. When I sold it this spring I had a few very small chunks that had come off on the top edge of the tailgate, just from shovels, etc.. They would have touched it up for me, but I had to leave the truck for the whole day and never could find the time to get someonw to drive up there, drop the truck off, etc.
If I had to do it again I'd consider linex. Also, I'd consider a couple drain holes being drilled before hand, and really well painted around the 2 holes underneath and then make sure they also hit it with the stuff underneath around the holes for full hole coverage on both sides.
Hope this helps.
--Bob