I'm looking to add a pair of 8's in my 08 nissan 350z enthusiast and i was wondering will i need to do any modding to the spots where the 8's will go into ?

 

You never said where you were planning on putting the 8's so yes, serious modification will be required

 

I plan on putting them in the stock spots right behind my head.

 

If you're planning on replacing the two 6.5" speakers in the rear shelf area, you'll need to modify the metal framework to fit an 8.0" speaker. You should also consult the FSM, as you'll need to pull all the rear plastic interior panels to get to that area.

 

2 8 inch what? Midbass? Subs?

 

Yes 8 inch subs

 

Then with subs you either need to find IB subs or fiberglass in the area in order to get them to function well sealed.

 

dont do it ! not worth the work time

 

I made a box and installed a shallow mount 12" behind the drivers seat that just sits in the cubby where the stock bose sub used to be. It cost me around $60 with the subwoofer