Not wanting to be a smart a$$ . First i would change out all of your windows for plexi glass.
Any way i would test only one sub with about a 3too4hundred watt amp bridged for sub in the small space of a cruiser you realy dont need more. im running a
Clarion DXZ935 head unit
Rockford Fosgate 61/4 in doors
Rockford Fosgate tweets mounted in corners of windshield
Boston FX8 5x7s in rear pillers
Rockford Fosgate 900 watt 4 chanel under front seat for main
Bazooka 300 watt 2 chanel bridged under rear shelf
Bazooka 8in sub that looks like an NOS bottle
Unless you want to rock the hood and get tickets for noise this system realy sounds good. Not so loud that it vibrates the metal panels of the car but i get a nice back massage from the seats vibrating.
IM FIFTY AND LOVE THE BOOM 
Also you want to hook with factory system all you will hear is boom . But all this is only my opinion talk to some friends and listen too other systems . And take your time and build slowly
I also have a 10in Bazooka tube that will rattle the doors. Most of all have fun. My wifes pt a 2001 has stock radio with Bazooka 300 watt amp with bass remote and an 8in Kicker substation box and sounds great.