I need wiring help...

I am attempting to add a stock rear entertainment system from a salvage 2003 Trailblazer to my 2003 trailblazer. The head unit wiring is no problem but I can't figure out the wiring configuration from the head unit plug to the plug on the rear overhead unit. I am going to make my own harness but I need to know which pins on the head unit plug connect to the pins on the rear display unit plug. Does anyone have or know where to get the pin out configurations for these two plugs??? Any help would be appreciated.