Which interface /Adapter do I need ?

[nujackk]

Hi all bought a used 04 AV Z71 about 3 weeks ago. I am planning on installing my D3  with and amp and 12" sub.
I know it has a bose system, with onstar and xm, and steering wheel controls.
Trying to find out which adapter/interface I need to get. PAC website only takes me to list of them I narrowed it down ( i hope correctly) to these two but not sure which I should get.  Any guidance you can provide will be greatly appreciated.

OS-2Bose  or   OS-4

 

[nujackk]

nobody? do you need more info?

[MS03 2500]

Well what is a D3 and what AMP and what sub are you installing. 

Details to get it right I don't follow the aftermarket stuff.

[midwest kid]

Straight off the PAC site. In order to retain steering wheel controls, you'll need an addition interface. Your D3 will provide SUB output for the amp.

Pacific Accessory Corporation OS-2 BOSE
OnStar® Interface for Class 2 vehicles with Bose® sound systems. Same as OS-2 above but without an onboard amplifier for OnStar® audio

Pacific Accessory Corporation SWI-PS
Steering Wheel Interface for Pioneer, Sony, Advent, Jensen & Dual

Well what is a D3 and what AMP and what sub are you installing. 

D3 is a Pioneer Double DIN Headunit.

[SurvivalFreak]

To retain the factory onstar, I had been told one needed a VERY expensive harness, "GMOS-11", of course that was for my 2002, so perhaps not applicable in your situation.  You will definatly need a high end harness if you have steering wheel controlls and want to retain that function as well as onStar.