even better if you are replacing speakers why not just run new speaker wires.

 

That is the route I would go. Good Luck!!!!

 

Would OnStar try to contact me with the Factory Radio Out? Since they can't contact me?

 

I used a regular GM harness with mine. I lost chimes and such. yippee. The regular harness is like 10 to 15 bucks depending on where you get it. If you are running an amp with aftermarket door speakers, you may wanna splice into the factory wiring behind the head unit for easy access. The doors are super pita to get wiring thru.