Ash is a beautiful wood, but lacks decay resistance. If the truck is going to be stored out in the elements, I would not recommend using ash for bed wood.
Emerald Ash Borer sucks.
Actually they bite
Yes that is true but with the right inish it can be protected. I made a mail box from ash and used marine spar varnish on it and as far as I know it is still lasting. I guess it all depends on the use of the truck.