New guy with a question...

I have a 03 Silverado RCSB with the 5.3. I bought a 6.0L for a different project, but realized that I also had the harness,ecu,etc, out of an 03 Silverado 2500(i'm guessing). I want to swap in the 6.0L...is it a straight swap? I know it will bolt in but will my harness plug into the rest? I do plan on putting in a 4L80e with a stall, is there an easy way to find out if my harness is for a 4L80e or 4l60e.

If you swap the 6.0 long block it's a direct fit no mods required. The 80e requires only mild modification thought tuning is required for both.

the tranny swap isnt to hard, i had to hook up 2 wires and add them to the pcm harness, and just added to the crossmember didnt even have to cut it. just make sure your converter is cut for a 4l60 flywheel unless your changing that too.