Spreader Material

I would like to know what is the preferred type of wood for building a replacement set of spreaders. I have a 27 foot Cal located in the PNW. The current spreaders have been up for over 15 years but we do not know what they are made out off. I'm thinking some kinda of hickory or walnut but do these woods have sufficient anti rot properties. We will be painting them and plan to repaint every year or so. So it should be a big deal but how much strength is needed verses longevity. If you have any experience on this topic it would be much appreciated.

Kindest Regards
Spreader Man