With your hubs having that much play in them, it actually helps, not hurts. Lemme get technical for a minute here.
You see, with all of that play in the hub, it allows the wheel to move in such a way so that is has less resistance and friction on it as compared to a "normal" hub. This results in lower rolling resistance which helps to increase efficiency, therefore netting you some extra mpg's. Typically, hubs like this only exist in high-end racecars (i.e. Nascar, F1, etc) but occasionally a rare phenomenon will occur with our standard hubs. It is called "Notzo-Tite," as it was the German's who first invented the hub. If you really do replace the hub, you could easily sell it on eBay for $10k, no questions asked. The fact that this happened shouldn't alarm you at all. I would drive that truck on a cross country trip like that with 100% faith in it, so you will be just fine for your short trip coming up.
If you want to get into the engineering side of it, shoot me a pm or a text. I'm always willing to pass along some knowledge to fellow enthusiast. :shake: