It would have to be whole new set up as any stock needs adapters as speakers and head unit are amped and will not mix without. Just leave tweeters and get componet kit for front and install subs in door and tweeters eother dash which gets reflection off window which is good or door panel which in kit will have template to cut.
If too much go to craigs and with somany out of work. their are people who would install for a lot less then store which charges like 60 radio, 40 for 2 speakers and 80 for an amp. I got a head unit, front component with 240 X 2 Amp. 3-6.5 Polk in back of front seats on side of SUV and 440 X 4 Amp, and 1 12" Rocksford 1000 watt Sub with 800 watt mono Amp and chaged 200.00 including some fiberglass and custom work with plexi glass.