Welcome to the site!!

I have never done the swap your doing, but I wish you all the luck!! I am swapping a 5.7 LS1 in my 04' Colorado, and I'm reusing the stock Colorado radiator but I also added dual electric fans from an F-body. As far as the wiring goes, a lot of people buy harnesses that are already modified which is fine. I think you learn a lot more if you do the wiring yourself but that's just me, someone will chime in about the specifics though....