Just having some thoughts here. I'm getting ready to replace the 19.5's on my truck and since this vibration issue came up I have been looking into issues more than usual. The wheels on our trucks are hub centric, some people replace wheels with ones that are stud centric OR the possibility arises that the hub centric wheels are not installed properly. Granted the tolerances are pretty tight and generally there shouldnt be a problem however without using a true balance tool, the possibility exists the wheel may not be properly balanced on the hub.
The issue I'm sure is enhanced with the larger wheels. Another thing I noticed is that when you search for lug nuts for our trucks, most of them come up as beveled which would make your wheel "stud centric". I have read several older threads that say a slight gap on a hub centric wheel will cause issues. People who have found the true balance tool have had great outcomes of their balance issues going away. I usually watch the mechanics when they are mounting my tires, I have never seen one use one of these tools while mounting my tires. You would think a tire shop would own these.
Anyway, food for thought...