Wood bed material suggestion

[400ex]

I need to replace whats left of my wood bed. I was thinking of buying some 3/4" sheets of wood from Lowes, Home Depot,etc.. Im not getting regular plywood. I was thinking something along the lines of a harder wood to withstand the weather for a few more years after coating it with something like linseed oil. Then maybe using using a router to cut some valleys for the metal strips to lay in. This is just a daily beater, nothing special.

I just dont know what type of wood to use. What do you guys suggest?

Thanks

James