I don't have the headliner installed in the Sprint yet. When I drive, I get a lot of air coming in from the large open spaces in the roof walls just below where the shoulder belts attach. Is this normal (meaning a headliner will eliminate it), or do I need to look for someplace where there is a big hole that needs to be plugged? The air comes in both sides.

Thanks all...

If you've got holes on your bed walls the air will move forward. If you bed floor and rear acess panels are sealed you shouldn't have much air movement once all int furnishings are in.
It would behoove you to add some sound deadener in those sail panel,headliner,and rear cabin areas. You wont be able to stop noise transmission thru the glass but knocking it down in other areas shure does help.