I would never use ash or oak for a truck that is to be used, and stored outdoors. IMO, wood is only for decorative/display purposes. If you want a be that is going to be functional and look good for a long time, it's got to be steel or aluminum.
Don't get me wrong - I love wood. It's my life. But I also recognize that it's not a universal answer. As with ANY project, determine what your objectives are first, and then begin to compromise. It's a rare project that doesn't have compromises of one sort or another...
