First is my correspondence with EmperorJJ1, this pretty much explains what you need to retain your steering wheel controls is the PAC SWI-PS or the PAC universal.

The second thing is the correspondence I got from Metra when it comes to retaining onstar:

This will be difficult to explain. If you do not understand this, please call.
What you will need is the 99-3303 kit, quantity two SP-2003 speakers, a 95-3302 kit, and a 40-GM10 antenna adapter. You will have to remove the harness and display off the 99-3303 kit, and disregard the plastic kit. Then hide the display somewhere in the dash where you will not see the lighting of the display. Then cut the white and grey speaker wires coming out of the 99-3303's interface, and send to the SP-2003 speakers under the dash where they will be mounted.

You have to use the 99-3303 because it is the only interface we have for that vehicle to retain Onstar. You have to cut the speaker wires out of the interface to have the built in amp in the interface power the speakers because you are installing an aftermarket amplifier.


Matt Calderon
Lead Tech
Metra Electronics Corp.
1-800-221-0932 #2328

I guess you maybe to use any old speaker instead of the provided part number and instead of putting the display behind the dash put it run underneath the double din in a custom mount. I'm going with a double din head unit and I'll probably put the metra display in the glove box.

 

awesome post, great info with all the answers in one place.

 

What if you are not installing an amp, just an aftermarket pioneer double din headunit to hook up to the stock pioneer sub and speakers? Can we bypass any of this?

 

are you looking to keep onstar? the main reason for doing any of that is to keep onstar. if thats not an issue then its somewhat easy to just add the pioneer double din