While we're only talking about an 8' popup here, we're also talking about long-distance travel. An F250/2500 type truck will guarantee that you will NEVER feel uncomfortable during the trip.
If you were limiting yourself to short local trips, I would say you could get by with an F150 or 1500. Your load-outs would be much lighter because you wouldn't be taking along weeks' worth of food and clothing. Plus you can tolerate any idiosyncrasies in the driving/handling qualities of the rig for an hour or two. When you have to put up with them for 6-8 hours a day, it can be tiring, leaving you with no energy to enjoy the destination.