Don, Bruce is right for a working truck. If you want it more for show, the traditional way is to cut oak to size and drill. Then sand and finish with spar varnish. Be sure to finish both sides of the wood and the end grain. If you are going to go to the work of 7-8 coats of finish, I would sure think about oak--costs a little more but will last a lot longer for either application. Which ever finish--spar varnish or poly--using the thinned coats to start will help a lot. Be sure to sand between all coats and tack rag. This will break up the surface gloss and allow additional coats to stick, preventing the flaking. Let us know how this comes out.