I have two beds that need replacement, looked into material from a hardwood store. Was directed to "quarter sawn" red oak.
When its cut like that the expansion and contraction with heat and cold is different from regular sawn planks.
The challenge is that you will have to have the planks milled to, I think, 5/8 from 3/4 thickness.
Seal on all sides with tung oil and I think I'll be good to go for a few more decades, well, at least the truck.