In the rear you can either put them into the parcel shelf or if you have really small speakers you could put them on either side of the parcel shelf where that pastic over hand is, id think only about a 4inch would fit in there, as for the front 4inch in the original holes.
Ive got a set of 4 inch spits and no rear speakers , but think ill have to get a really small sub just to balance the sound out, bit to much treble