Truck bounces around when driving between 35-40 mph

Does the truck seem to bounce only when hitting bumps or is it a continual bounce condition during that speed range?

Thanks for the clarification. Vibrations or bouncing that occurs only in certain speed ranges is almost always caused by tire imbalance. At this point, I suggest having your tires re-balanced by a local tire dealer. If the tires are significantly worn or worn unevenly, this could also be a contributor to the vibration. If that's the case, they most likely would need to be replaced.

Worn suspension components or bushings normally don't cause this type of condition. It certainly wouldn't hurt to go through all the suspension bushings and joints to check for wear/play, however I don't think that's the cause of your issue.

When they balanced your tires, do you know if they performed a "road force" balance? This is different from a standard tire balance as it measures the amount of force exerted against the road surface by the tire. Certain tire issues won't be identified by a normal balance. I would recommend having this done if it wasn't already performed.

It is possible there is an issue with that wheel too. This is something a road force balance would identify.

Have you tried moving that wheel/tire to a different position on the truck to see if the issue follows it? That’s something quick and easy to try before going back to the tire store.

Sounds good.