RWG

My Aciv-z1 was installed in a 2003 Silverado LT and everything worked great. I traded trucks and had the Avic-Z1 re-installed in a 2008 Silverado XLT. The installer (shop where I purchased it) is telling me that the control for the 2008 truck is not available. So I am looking for the controls needed to hook up the streeing wheel controls for a 2008 Silverado XLT to the Avic-z1. Can anyone help?