For those of you looking to replace rear speakers, while maintaining the factory amp and wiring, it's possible and not that hard.

I put in 5 1/4 coaxial speakers, and split the speaker wiring to wire the tweeter and woofer directly into the stock harness. Tip, use the butt connectors with solder core, as the wire is super small gauge and hard to crimp. Then, I made a mounting plate to create a flat surface to mount to in the car, I used a thin plastic cutting board for the material and it worked great.

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