I hate to tell you this, but the BEST thing you can do, is if you are replacing all the speakers, and adding new amps, then RUN ALL NEW WIRES. Every time I splice into factory OEM wiring, there is a big chance of induced noise. Also, I have even seen (not necessarily the case here) same year cars with different color wiring schemes. To say which wire is which may mislead you. Get out your multimeter and test the wires to see if they are power, ground, signal or speaker wires. Then use a battery to "pop" each pair of speaker wires to test which speaker is which.
This can all get very confusing, and again, I strongly recommend running new wires, directly from your new amps to your new speakers. It is more work, but defintely worth it if anything should ever go wrong.