I have the 2008 cutaway van with 6.0 motor and cannot figure out the part numbers for the downstream O2 sensors, it almost looks like there are two different part numbers, one GM site shows position two and three???

GM won't tell you the part numbers anymore, so does anyone have a way to access that?
last 8 on my vin 81111071

 

You should be able to look up diagrams on GMpartsdirect.com

 

they are the same o2 sensor . the reason for two numbers is the length of the wire..