Best wood for my truck??

[67pro-street]

I am planning on putting in a wood bed for my truck, but i was wondering what type would best suit me. I live in the pacafic northwest, so we get a lot of rain, but i am planning on having a soft tonneau on the truck. My truck will also be outside year-round. It will have a roof over it, but thats about all the protection it will get, so it will have lots of temp. fluctuations and what not. I have heard that oak wood will stain easily when water gets under the varnish. Is this true??? One more thing, i will not be carrying anything in the bed, so strength is not a major factor...for the most part. sorry for the bombardment of questions, but any help would be greatly appreciated.

67pro-street