I have already submitted my $0.02, can I put in two more?
While Mahogany is technically a hard wood, it is soft in comparison to many other "hard" woods. I still think it would be a good looking bed, but not durable for a work truck. That said, it would probably last fine, but look really bad after it is nicked and scratched repeatedly. A physically harder wood, like oak, will look better for longer if the truck is used as a truck.
Most all woods will cup if you choose the right grain orientation to allow it to do so. for oak it won't cup at all if it is finished in the same way the same on both sides, and it is true "quarter sawn". Quarter sawn wood is like looking at the end of the log and taking a piece of pie out of it, and make that piece parallel in thickness, not a piece of pie now, but you get the idea of how it comes from the tree. Generally quarter sawn wood is more stable, but some woods benefit from it more than others, it really helps oak to stay flat.
For my truck, a real work truck, and also for show, I will use quarter sawn white oak. It will stay flat, last a long time, and look great. Many other types of oak are not rot resistant like white oak is. Being quarter sawn will make it look great, and help prevent cupping. I will also allow space between the boards for them to swell and contract without binding and forcing a cup. The SS strips will hold them down, and mask the unavoidable seasonal movements (changes in width) length changes very little with moisture changes. SS as opposed to regular steel will look better because dark stains won't form where the oak touches the metal.
Another important thing when choosing wood is to be sure it is dry, but not to dry. Best to let it sit in the shop and normalize for a few months if you can.
I go to get my bed wood this week, it will be green, so I will stack it and sticker it to dry, and tie the bundle together with ratchet straps to keep them flat, snugging them up regularly. in a few years when I am ready to use them I'll joint, rip, and plane to final thickness.
There are so many wood choices out there, and some I think are better over all than oak. Even though I could get most of these different, fancier, and/or imported woods, white oak is the look and durability I want for my truck.
For as many different kinds of people and their trucks, there are probably that many wood choices too, so pick the one you like for whatever the reasons, but it can't hurt to do some research on it's quality's before the final decision.
That may have been $0.04, oops

Grigg