Just to update regarding location of rattle. By lucky coincidence I landed rather hard on the fiberglass running board and found that it changed the sound of the rattle. As it turns out, the space where the runningboard contacts the body can cause a rattle which is really, really hard to pinpoint. It isn't rattleing now but the suggestion of applying silicone caulk would probably cure it if it starts again.
We lost both front tires on the way back from Illinois to Fort Myers. They were originals (22K miles) and nearly full tread. Tread separated from casing but did not lose air. In each case I called for road service to change tire. Expensive but I didn't want to carry the tools or hassle with the big tires. Fronts are now E rated and am shopping for a nice soft set for the duallies.