Gates was/is the GM supplier for both Belt Tensioners and the Idler Pulley for all four years of the SSR, both 5.3 and 6.0 liter applications. You can see traces of that connection when comparing the part numbering between AC Delco and Gates.
_______________GM___AC Delco__Gates
AC Tensioner  12580196  38159  38159
Main Tensioner 12609719  38158  38158
Idler Pulley     12669569  36299  36299
Please note that your part may come with either Gates or AC Delco packaging.
