I'm trying to research any differences between harnesses of a 2004 2wd 4.3l blazer base model with a/c and my 2001 crew cab with of course 4wd, cruise, and a/c. My current engine is in pretty bad shape and pretty sure the car lot my wife bought it from got a used engine from a salvage yard with all the zip ties holding wiring in place. My buddy had a wreck in his 04 blazer but motor survived. It runs really strong and hasn't had any check engine lights prior to the wreck. I know his motor doesn't have egr or secondary air and discovered the other day that the O2 sensor plugs are different, the knock sensor is different, as well as PCM number. My hopes are to use the motor, harness, and PCM in my truck after having my vin flashed into PCM. I found wiring diagrams for the 2004 online but haven't had any luck on diagrams for my truck to compare against the 04. Can anybody think of anything else that is or might be different between the two?