as long as you have a filler up front and not just those 8's you will be fine for sound. You could also do some 8" memphis m-sync components, they are a lil bit shallower than the z-series, but still great quality. Plus they are not just midbass drivers, they are full blown components. I had those in my silverado plus a set of 6.5" in the kicks and it sounded great (along with other stuff of course, haha).

Have you got anything in the car now, audio wise?