like king said make a ring to go extend the protection of the speaker
or recess the speaker into the box this would be my choice
if it's a carpeted box this would be easy to do, a little more challenging if it's painted
not a good pic but i recessed my ring when i made the box
if you have your seat all the way forward the box is wrong for your truck
while i made mine to fit my 58 this would be an easy box to adapt to any truck
i'm tall and designed this box to have the seat against the back window